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1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </div> <div class=md-source__repository> flokoe/bash-hackers-wiki </div> </a> </div> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../.. class=md-nav__link> <span class=md-ellipsis> Start </span> </a> </li> <li class="md-nav__item md-nav__item--active md-nav__item--section md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_2 checked> <label class=md-nav__link for=__nav_2 id=__nav_2_label tabindex> <span class=md-ellipsis> Commands </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_2_label aria-expanded=true> <label class=md-nav__title for=__nav_2> <span class="md-nav__icon md-icon"></span> Commands </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../classictest/ class=md-nav__link> <span class=md-ellipsis> The classic test command </span> </a> </li> <li class="md-nav__item md-nav__item--active md-nav__item--section md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_2_2 checked> <label class=md-nav__link for=__nav_2_2 id=__nav_2_2_label tabindex> <span class=md-ellipsis> Builtin </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_2_2_label aria-expanded=true> <label class=md-nav__title for=__nav_2_2> <span class="md-nav__icon md-icon"></span> Builtin </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../caller/ class=md-nav__link> <span class=md-ellipsis> The caller builtin command </span> </a> </li> <li class=md-nav__item> <a href=../cd/ class=md-nav__link> <span class=md-ellipsis> The cd builtin command </span> </a> </li> <li class=md-nav__item> <a href=../declare/ class=md-nav__link> <span class=md-ellipsis> The declare builtin command </span> </a> </li> <li class=md-nav__item> <a href=../echo/ class=md-nav__link> <span class=md-ellipsis> The echo builtin command </span> </a> </li> <li class=md-nav__item> <a href=../eval/ class=md-nav__link> <span class=md-ellipsis> The eval builtin command </span> </a> </li> <li class=md-nav__item> <a href=../exec/ class=md-nav__link> <span class=md-ellipsis> The exec builtin command </span> </a> </li> <li class=md-nav__item> <a href=../exit/ class=md-nav__link> <span class=md-ellipsis> The exit builtin command </span> </a> </li> <li class=md-nav__item> <a href=../export/ class=md-nav__link> <span class=md-ellipsis> The export builtin command </span> </a> </li> <li class=md-nav__item> <a href=../kill/ class=md-nav__link> <span class=md-ellipsis> The kill builtin command </span> </a> </li> <li class=md-nav__item> <a href=../let/ class=md-nav__link> <span class=md-ellipsis> The let builtin command </span> </a> </li> <li class=md-nav__item> <a href=../local/ class=md-nav__link> <span class=md-ellipsis> The local builtin command </span> </a> </li> <li class=md-nav__item> <a href=../mapfile/ class=md-nav__link> <span class=md-ellipsis> The mapfile builtin command </span> </a> </li> <li class="md-nav__item md-nav__item--active"> <input class="md-nav__toggle md-toggle" type=checkbox id=__toc> <label class="md-nav__link md-nav__link--active" for=__toc> <span class=md-ellipsis> The printf command </span> <span class="md-nav__icon md-icon"></span> </label> <a href=./ class="md-nav__link md-nav__link--active"> <span class=md-ellipsis> The printf command </span> </a> <nav class="md-nav md-nav--secondary" aria-label="Table of contents"> <label class=md-nav__title for=__toc> <span class="md-nav__icon md-icon"></span> Table of contents </label> <ul class=md-nav__list data-md-component=toc data-md-scrollfix> <li class=md-nav__item> <a href=#general class=md-nav__link> <span class=md-ellipsis> General </span> </a> </li> <li class=md-nav__item> <a href=#syntax class=md-nav__link> <span class=md-ellipsis> Syntax </span> </a> <nav class=md-nav aria-label=Syntax> <ul class=md-nav__list> <li class=md-nav__item> <a href=#options class=md-nav__link> <span class=md-ellipsis> Options </span> </a> </li> <li class=md-nav__item> <a href=#arguments class=md-nav__link> <span class=md-ellipsis> Arguments </span> </a> </li> <li class=md-nav__item> <a href=#format-strings class=md-nav__link> <span class=md-ellipsis> Format strings </span> </a> </li> <li class=md-nav__item> <a href=#modifiers class=md-nav__link> <span class=md-ellipsis> Modifiers </span> </a> <nav class=md-nav aria-label=Modifiers> <ul class=md-nav__list> <li class=md-nav__item> <a href=#field-and-printing-modifiers class=md-nav__link> <span class=md-ellipsis> Field and printing modifiers </span> </a> </li> <li class=md-nav__item> <a href=#precision class=md-nav__link> <span class=md-ellipsis> Precision </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#escape-codes class=md-nav__link> <span class=md-ellipsis> Escape codes </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#examples class=md-nav__link> <span class=md-ellipsis> Examples </span> </a> <nav class=md-nav aria-label=Examples> <ul class=md-nav__list> <li class=md-nav__item> <a href=#snipplets class=md-nav__link> <span class=md-ellipsis> Snipplets </span> </a> </li> <li class=md-nav__item> <a href=#small-code-table class=md-nav__link> <span class=md-ellipsis> Small code table </span> </a> </li> <li class=md-nav__item> <a href=#ensure-well-formatted-mac-address class=md-nav__link> <span class=md-ellipsis> Ensure well-formatted MAC address </span> </a> </li> <li class=md-nav__item> <a href=#replacement-echo class=md-nav__link> <span class=md-ellipsis> Replacement echo </span> </a> </li> <li class=md-nav__item> <a href=#prargs-implementation class=md-nav__link> <span class=md-ellipsis> prargs Implementation </span> </a> </li> <li class=md-nav__item> <a href=#repeating-a-character-for-example-to-print-a-line class=md-nav__link> <span class=md-ellipsis> repeating a character (for example to print a line) </span> </a> </li> <li class=md-nav__item> <a href=#replacement-for-some-calls-to-date1 class=md-nav__link> <span class=md-ellipsis> Replacement for some calls to date(1) </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#differences-from-awk-printf class=md-nav__link> <span class=md-ellipsis> differences from awk printf </span> </a> </li> <li class=md-nav__item> <a href=#differences-from-c-and-portability-considerations class=md-nav__link> <span class=md-ellipsis> Differences from C, and portability considerations </span> </a> </li> <li class=md-nav__item> <a href=#see-also class=md-nav__link> <span class=md-ellipsis> See also </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../read/ class=md-nav__link> <span class=md-ellipsis> The read builtin command </span> </a> </li> <li class=md-nav__item> <a href=../readonly/ class=md-nav__link> <span class=md-ellipsis> The readonly builtin command </span> </a> </li> <li class=md-nav__item> <a href=../return/ class=md-nav__link> <span class=md-ellipsis> The return builtin command </span> </a> </li> <li class=md-nav__item> <a href=../set/ class=md-nav__link> <span class=md-ellipsis> The set builtin command </span> </a> </li> <li class=md-nav__item> <a href=../shift/ class=md-nav__link> <span class=md-ellipsis> The shift builtin command </span> </a> </li> <li class=md-nav__item> <a href=../shopt/ class=md-nav__link> <span class=md-ellipsis> The shopt builtin command </span> </a> </li> <li class=md-nav__item> <a href=../trap/ class=md-nav__link> <span class=md-ellipsis> The trap builtin command </span> </a> </li> <li class=md-nav__item> <a href=../unset/ class=md-nav__link> <span class=md-ellipsis> The unset builtin command </span> </a> </li> <li class=md-nav__item> <a href=../wait/ class=md-nav__link> <span class=md-ellipsis> The wait builtin command </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_3> <label class=md-nav__link for=__nav_3 id=__nav_3_label tabindex=0> <span class=md-ellipsis> Dict </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_3_label aria-expanded=false> <label class=md-nav__title for=__nav_3> <span class="md-nav__icon md-icon"></span> Dict </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../dict/directory/ class=md-nav__link> <span class=md-ellipsis> Directory </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/end_of_options/ class=md-nav__link> <span class=md-ellipsis> End of Options </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/exit_status/ class=md-nav__link> <span class=md-ellipsis> Exit Status </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/file/ class=md-nav__link> <span class=md-ellipsis> File </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/filetimes/ class=md-nav__link> <span class=md-ellipsis> File timestamp </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/globbing/ class=md-nav__link> <span class=md-ellipsis> Globbing </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/hardlink/ class=md-nav__link> <span class=md-ellipsis> Hardlink </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/interpreter_directive/ class=md-nav__link> <span class=md-ellipsis> Interpreter Directive </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/parameter/ class=md-nav__link> <span class=md-ellipsis> Parameter </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/posix/ class=md-nav__link> <span class=md-ellipsis> POSIX </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/shell/ class=md-nav__link> <span class=md-ellipsis> Shell </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/special_file/ class=md-nav__link> <span class=md-ellipsis> Special file </span> </a> </li> <li class=md-nav__item> <a href=../../../dict/symlink/ class=md-nav__link> <span class=md-ellipsis> Symlink </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4> <label class=md-nav__link for=__nav_4 id=__nav_4_label tabindex=0> <span class=md-ellipsis> Howto </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_4_label aria-expanded=false> <label class=md-nav__title for=__nav_4> <span class="md-nav__icon md-icon"></span> Howto </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../howto/calculate-dc/ class=md-nav__link> <span class=md-ellipsis> Calculating with dc </span> </a> </li> <li class=md-nav__item> <a href=../../../howto/collapsing_functions/ class=md-nav__link> <span class=md-ellipsis> Collapsing Functions </span> </a> </li> <li class=md-nav__item> <a href=../../../howto/conffile/ class=md-nav__link> <span class=md-ellipsis> Config files for your script </span> </a> </li> <li class=md-nav__item> <a href=../../../howto/dissectabadoneliner/ class=md-nav__link> <span class=md-ellipsis> Dissect a bad oneliner </span> </a> </li> <li class=md-nav__item> <a href=../../../howto/edit-ed/ class=md-nav__link> <span class=md-ellipsis> Editing files via scripts with ed </span> </a> </li> <li class=md-nav__item> <a href=../../../howto/getopts_tutorial/ class=md-nav__link> <span class=md-ellipsis> Small getopts tutorial </span> </a> </li> <li class=md-nav__item> <a href=../../../howto/mutex/ class=md-nav__link> <span class=md-ellipsis> Lock your script (against parallel execution) </span> </a> </li> <li class=md-nav__item> <a href=../../../howto/pax/ class=md-nav__link> <span class=md-ellipsis> pax - the POSIX archiver </span> </a> </li> <li class=md-nav__item> <a href=../../../howto/redirection_tutorial/ class=md-nav__link> <span class=md-ellipsis> Illustrated Redirection Tutorial </span> </a> </li> <li class=md-nav__item> <a href=../../../howto/testing-your-scripts/ class=md-nav__link> <span class=md-ellipsis> Testing your scripts </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_5> <label class=md-nav__link for=__nav_5 id=__nav_5_label tabindex=0> <span class=md-ellipsis> Internals </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_5_label aria-expanded=false> <label class=md-nav__title for=__nav_5> <span class="md-nav__icon md-icon"></span> Internals </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../internals/shell_options/ class=md-nav__link> <span class=md-ellipsis> List of shell options </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_6> <label class=md-nav__link for=__nav_6 id=__nav_6_label tabindex=0> <span class=md-ellipsis> Misc </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_6_label aria-expanded=false> <label class=md-nav__title for=__nav_6> <span class="md-nav__icon md-icon"></span> Misc </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../misc/bashphorisms/ class=md-nav__link> <span class=md-ellipsis> The Bashphorisms </span> </a> </li> <li class=md-nav__item> <a href=../../../misc/readthesourceluke/ class=md-nav__link> <span class=md-ellipsis> Readthesourceluke </span> </a> </li> <li class=md-nav__item> <a href=../../../misc/shell_humor/ class=md-nav__link> <span class=md-ellipsis> Shell Humor </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_7> <label class=md-nav__link for=__nav_7 id=__nav_7_label tabindex=0> <span class=md-ellipsis> Scripting </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_7_label aria-expanded=false> <label class=md-nav__title for=__nav_7> <span class="md-nav__icon md-icon"></span> Scripting </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../scripting/bashbehaviour/ class=md-nav__link> <span class=md-ellipsis> Bash's behaviour </span> </a> </li> <li class=md-nav__item> <a href=../../../scripting/bashchanges/ class=md-nav__link> <span class=md-ellipsis> Bash changes </span> </a> </li> <li class=md-nav__item> <a href=../../../scripting/basics/ class=md-nav__link> <span class=md-ellipsis> The basics of shell scripting </span> </a> </li> <li class=md-nav__item> <a href=../../../scripting/debuggingtips/ class=md-nav__link> <span class=md-ellipsis> Debugging a script </span> </a> </li> <li class=md-nav__item> <a href=../../../scripting/newbie_traps/ class=md-nav__link> <span class=md-ellipsis> Beginner Mistakes </span> </a> </li> <li class=md-nav__item> <a href=../../../scripting/nonportable/ class=md-nav__link> <span class=md-ellipsis> Portability talk </span> </a> </li> <li class=md-nav__item> <a href=../../../scripting/obsolete/ class=md-nav__link> <span class=md-ellipsis> Obsolete and deprecated syntax </span> </a> </li> <li class=md-nav__item> <a href=../../../scripting/posparams/ class=md-nav__link> <span class=md-ellipsis> Handling positional parameters </span> </a> </li> <li class=md-nav__item> <a href=../../../scripting/processtree/ class=md-nav__link> <span class=md-ellipsis> Bash and the process tree </span> </a> </li> <li class=md-nav__item> <a href=../../../scripting/style/ class=md-nav__link> <span class=md-ellipsis> Scripting with style </span> </a> </li> <li class=md-nav__item> <a href=../../../scripting/terminalcodes/ class=md-nav__link> <span class=md-ellipsis> Terminal codes (ANSI/VT100) introduction </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_8> <label class=md-nav__link for=__nav_8 id=__nav_8_label tabindex=0> <span class=md-ellipsis> Snipplets </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_8_label aria-expanded=false> <label class=md-nav__title for=__nav_8> <span class="md-nav__icon md-icon"></span> Snipplets </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../snipplets/ class=md-nav__link> <span class=md-ellipsis> Small code snipplets </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/add_color_to_your_scripts/ class=md-nav__link> <span class=md-ellipsis> Add Color to your scripts </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/awkcsv/ class=md-nav__link> <span class=md-ellipsis> Using awk to deal with CSV that uses quoted/unquoted delimiters </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/filesize/ class=md-nav__link> <span class=md-ellipsis> Show size of a file </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/kill_bg_job_without_message/ class=md-nav__link> <span class=md-ellipsis> Kill a background job without a message </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/largestfile/ class=md-nav__link> <span class=md-ellipsis> Get largest file </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/pause_command/ class=md-nav__link> <span class=md-ellipsis> Pausing a script (like MSDOS pause command) </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/prargs/ class=md-nav__link> <span class=md-ellipsis> Print argument list for testing </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/print_horizontal_line/ class=md-nav__link> <span class=md-ellipsis> Print a horizontal line </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/rndstr/ class=md-nav__link> <span class=md-ellipsis> Print a random string or select random elements </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/screen_saverestore/ class=md-nav__link> <span class=md-ellipsis> Save and restore terminal/screen content </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/ssh_fetchkeys/ class=md-nav__link> <span class=md-ellipsis> Fetching SSH hostkeys without interaction </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/ssh_local_var/ class=md-nav__link> <span class=md-ellipsis> Run some bash commands with SSH remotely using local variables </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/wrapperargs/ class=md-nav__link> <span class=md-ellipsis> Generate code with own arguments properly quoted </span> </a> </li> <li class=md-nav__item> <a href=../../../snipplets/xclip/ class=md-nav__link> <span class=md-ellipsis> X-Clipboard on Commandline </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_9> <label class=md-nav__link for=__nav_9 id=__nav_9_label tabindex=0> <span class=md-ellipsis> Syntax </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_9_label aria-expanded=false> <label class=md-nav__title for=__nav_9> <span class="md-nav__icon md-icon"></span> Syntax </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../syntax/arith_expr/ class=md-nav__link> <span class=md-ellipsis> Arithmetic expressions </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/arrays/ class=md-nav__link> <span class=md-ellipsis> Arrays </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/basicgrammar/ class=md-nav__link> <span class=md-ellipsis> Basic grammar rules of Bash </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/pattern/ class=md-nav__link> <span class=md-ellipsis> Patterns and pattern matching </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/pe/ class=md-nav__link> <span class=md-ellipsis> Parameter expansion </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/quoting/ class=md-nav__link> <span class=md-ellipsis> Quotes and escaping </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/redirection/ class=md-nav__link> <span class=md-ellipsis> Redirection </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/shellvars/ class=md-nav__link> <span class=md-ellipsis> Special parameters and shell variables </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/words/ class=md-nav__link> <span class=md-ellipsis> Words... </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_9_10> <label class=md-nav__link for=__nav_9_10 id=__nav_9_10_label tabindex=0> <span class=md-ellipsis> Ccmd </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_9_10_label aria-expanded=false> <label class=md-nav__title for=__nav_9_10> <span class="md-nav__icon md-icon"></span> Ccmd </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../syntax/ccmd/arithmetic_eval/ class=md-nav__link> <span class=md-ellipsis> Arithmetic evaluation (command) </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/ccmd/c_for/ class=md-nav__link> <span class=md-ellipsis> The C-style for-loop </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/ccmd/case/ class=md-nav__link> <span class=md-ellipsis> The case statement </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/ccmd/classic_for/ class=md-nav__link> <span class=md-ellipsis> The classic for-loop </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/ccmd/conditional_expression/ class=md-nav__link> <span class=md-ellipsis> The conditional expression </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/ccmd/grouping_plain/ class=md-nav__link> <span class=md-ellipsis> Grouping commands </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/ccmd/grouping_subshell/ class=md-nav__link> <span class=md-ellipsis> Grouping commands in a subshell </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/ccmd/if_clause/ class=md-nav__link> <span class=md-ellipsis> The if-clause </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/ccmd/intro/ class=md-nav__link> <span class=md-ellipsis> Bash compound commands </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/ccmd/until_loop/ class=md-nav__link> <span class=md-ellipsis> The until loop </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/ccmd/user_select/ class=md-nav__link> <span class=md-ellipsis> User selections </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/ccmd/while_loop/ class=md-nav__link> <span class=md-ellipsis> The while-loop </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_9_11> <label class=md-nav__link for=__nav_9_11 id=__nav_9_11_label tabindex=0> <span class=md-ellipsis> Expansion </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_9_11_label aria-expanded=false> <label class=md-nav__title for=__nav_9_11> <span class="md-nav__icon md-icon"></span> Expansion </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../syntax/expansion/arith/ class=md-nav__link> <span class=md-ellipsis> Arithmetic expansion </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/expansion/brace/ class=md-nav__link> <span class=md-ellipsis> Brace expansion </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/expansion/cmdsubst/ class=md-nav__link> <span class=md-ellipsis> Command substitution </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/expansion/globs/ class=md-nav__link> <span class=md-ellipsis> Pathname expansion (globbing) </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/expansion/intro/ class=md-nav__link> <span class=md-ellipsis> Expansions and substitutions </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/expansion/proc_subst/ class=md-nav__link> <span class=md-ellipsis> Process substitution </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/expansion/tilde/ class=md-nav__link> <span class=md-ellipsis> Tilde expansion </span> </a> </li> <li class=md-nav__item> <a href=../../../syntax/expansion/wordsplit/ class=md-nav__link> <span class=md-ellipsis> Word splitting </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_9_12> <label class=md-nav__link for=__nav_9_12 id=__nav_9_12_label tabindex=0> <span class=md-ellipsis> Grammar </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_9_12_label aria-expanded=false> <label class=md-nav__title for=__nav_9_12> <span class="md-nav__icon md-icon"></span> Grammar </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../syntax/grammar/parser_exec/ class=md-nav__link> <span class=md-ellipsis> Parser exec </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_9_13> <label class=md-nav__link for=__nav_9_13 id=__nav_9_13_label tabindex=0> <span class=md-ellipsis> Keywords </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_9_13_label aria-expanded=false> <label class=md-nav__title for=__nav_9_13> <span class="md-nav__icon md-icon"></span> Keywords </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../syntax/keywords/coproc/ class=md-nav__link> <span class=md-ellipsis> The coproc keyword </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../../tags/ class=md-nav__link> <span class=md-ellipsis> Tags </span> </a> </li> </ul> </nav> </div> </div> </div> <div class="md-sidebar md-sidebar--secondary" data-md-component=sidebar data-md-type=toc> <div class=md-sidebar__scrollwrap> <div class=md-sidebar__inner> <nav class="md-nav md-nav--secondary" aria-label="Table of contents"> <label class=md-nav__title for=__toc> <span class="md-nav__icon md-icon"></span> Table of contents </label> <ul class=md-nav__list data-md-component=toc data-md-scrollfix> <li class=md-nav__item> <a href=#general class=md-nav__link> <span class=md-ellipsis> General </span> </a> </li> <li class=md-nav__item> <a href=#syntax class=md-nav__link> <span class=md-ellipsis> Syntax </span> </a> <nav class=md-nav aria-label=Syntax> <ul class=md-nav__list> <li class=md-nav__item> <a href=#options class=md-nav__link> <span class=md-ellipsis> Options </span> </a> </li> <li class=md-nav__item> <a href=#arguments class=md-nav__link> <span class=md-ellipsis> Arguments </span> </a> </li> <li class=md-nav__item> <a href=#format-strings class=md-nav__link> <span class=md-ellipsis> Format strings </span> </a> </li> <li class=md-nav__item> <a href=#modifiers class=md-nav__link> <span class=md-ellipsis> Modifiers </span> </a> <nav class=md-nav aria-label=Modifiers> <ul class=md-nav__list> <li class=md-nav__item> <a href=#field-and-printing-modifiers class=md-nav__link> <span class=md-ellipsis> Field and printing modifiers </span> </a> </li> <li class=md-nav__item> <a href=#precision class=md-nav__link> <span class=md-ellipsis> Precision </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#escape-codes class=md-nav__link> <span class=md-ellipsis> Escape codes </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#examples class=md-nav__link> <span class=md-ellipsis> Examples </span> </a> <nav class=md-nav aria-label=Examples> <ul class=md-nav__list> <li class=md-nav__item> <a href=#snipplets class=md-nav__link> <span class=md-ellipsis> Snipplets </span> </a> </li> <li class=md-nav__item> <a href=#small-code-table class=md-nav__link> <span class=md-ellipsis> Small code table </span> </a> </li> <li class=md-nav__item> <a href=#ensure-well-formatted-mac-address class=md-nav__link> <span class=md-ellipsis> Ensure well-formatted MAC address </span> </a> </li> <li class=md-nav__item> <a href=#replacement-echo class=md-nav__link> <span class=md-ellipsis> Replacement echo </span> </a> </li> <li class=md-nav__item> <a href=#prargs-implementation class=md-nav__link> <span class=md-ellipsis> prargs Implementation </span> </a> </li> <li class=md-nav__item> <a href=#repeating-a-character-for-example-to-print-a-line class=md-nav__link> <span class=md-ellipsis> repeating a character (for example to print a line) </span> </a> </li> <li class=md-nav__item> <a href=#replacement-for-some-calls-to-date1 class=md-nav__link> <span class=md-ellipsis> Replacement for some calls to date(1) </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#differences-from-awk-printf class=md-nav__link> <span class=md-ellipsis> differences from awk printf </span> </a> </li> <li class=md-nav__item> <a href=#differences-from-c-and-portability-considerations class=md-nav__link> <span class=md-ellipsis> Differences from C, and portability considerations </span> </a> </li> <li class=md-nav__item> <a href=#see-also class=md-nav__link> <span class=md-ellipsis> See also </span> </a> </li> </ul> </nav> </div> </div> </div> <div class=md-content data-md-component=content> <article class="md-content__inner md-typeset"> <a href=https://github.com/flokoe/bash-hackers-wiki/edit/main/docs/commands/builtin/printf.md title="Edit this page" class="md-content__button md-icon"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M10 20H6V4h7v5h5v3.1l2-2V8l-6-6H6c-1.1 0-2 .9-2 2v16c0 1.1.9 2 2 2h4zm10.2-7c.1 0 .3.1.4.2l1.3 1.3c.2.2.2.6 0 .8l-1 1-2.1-2.1 1-1c.1-.1.2-.2.4-.2m0 3.9L14.1 23H12v-2.1l6.1-6.1z"/></svg> </a> <a href=https://github.com/flokoe/bash-hackers-wiki/raw/main/docs/commands/builtin/printf.md title="View source of this page" class="md-content__button md-icon"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M17 18c.56 0 1 .44 1 1s-.44 1-1 1-1-.44-1-1 .44-1 1-1m0-3c-2.73 0-5.06 1.66-6 4 .94 2.34 3.27 4 6 4s5.06-1.66 6-4c-.94-2.34-3.27-4-6-4m0 6.5a2.5 2.5 0 0 1-2.5-2.5 2.5 2.5 0 0 1 2.5-2.5 2.5 2.5 0 0 1 2.5 2.5 2.5 2.5 0 0 1-2.5 2.5M9.27 20H6V4h7v5h5v4.07c.7.08 1.36.25 2 .49V8l-6-6H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h4.5a8.2 8.2 0 0 1-1.23-2"/></svg> </a> <h1 id=the-printf-command>The printf command<a class=headerlink href=#the-printf-command title="Permanent link">&para;</a></h1> <div class="admonition warning"> <p class=admonition-title>FIXME</p> <p>This is a very big topic that needs experience - please fill in missing information, extend the descriptions, and correct the details if you can!</p> </div> <div class="admonition info"> <p class=admonition-title>Bash-Builtin</p> <p>This is about the Bash-builtin command <code>printf</code> - however, the description should be nearly identical for an external command that follows POSIX&reg;.</p> <p><a href=http://www.gnu.org/software/gawk/manual/gawk.html#Printf>GNU Awk</a> expects a comma after the format string and between each of the arguments of a <strong>printf</strong> command. For examples, see: <a href=#differences-from-awk-printf>code snippet</a>.</p> </div> <p>Unlike other documentations, I don't want to redirect you to the manual page for the <code>printf()</code> C function family. However, if you're more experienced, that should be the most detailed description for the format strings and modifiers.</p> <p>Due to conflicting historical implementations of the <code>echo</code> command, POSIX&reg; recommends that <code>printf</code> is preferred over <code>echo</code>.</p> <h2 id=general>General<a class=headerlink href=#general title="Permanent link">&para;</a></h2> <p>The <code>printf</code> command provides a method to print preformatted text similar to the <code>printf()</code> system interface (C function). It's meant as successor for <code>echo</code> and has far more features and possibilities.</p> <p>Beside other reasons, POSIX&reg; has a very good argument to recommend it: Both historical main flavours of the <code>echo</code> command are mutual exclusive, they collide. A "new" command had to be invented to solve the issue.</p> <h2 id=syntax>Syntax<a class=headerlink href=#syntax title="Permanent link">&para;</a></h2> <div class=highlight><pre><span></span><code>printf &lt;FORMAT&gt; &lt;ARGUMENTS...&gt;
</code></pre></div> <p>The text format is given in <code>&lt;FORMAT&gt;</code>, while all arguments the formatstring may point to are given after that, here, indicated by <code>&lt;ARGUMENTS...&gt;</code>.</p> <p>Thus, a typical <code>printf</code>-call looks like:</p> <div class=highlight><pre><span></span><code>printf &quot;Surname: %s\nName: %s\n&quot; &quot;$SURNAME&quot; &quot;$FIRSTNAME&quot;
</code></pre></div> <p>where <code>"Surname: %s\nName: %s\n"</code> is the format specification, and the two variables are passed as arguments, the <code>%s</code> in the formatstring points to (for every format specifier you give, <code>printf</code> awaits one argument!).</p> <h3 id=options>Options<a class=headerlink href=#options title="Permanent link">&para;</a></h3> <table> <thead> <tr> <th>Option</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td><code>-v VAR</code></td> <td>If given, the output is assigned to the variable <code>VAR</code> instead of printed to <code>stdout</code> (comparable to <code>sprintf()</code> in some way)</td> </tr> </tbody> </table> <p>The <code>-v</code> Option can't assign directly to array indexes in Bash versions older than Bash 4.1.</p> <div class="admonition danger"> <p class=admonition-title>Danger</p> <p>In versions newer than 4.1, one must be careful when performing expansions into the first non-option argument of printf as this opens up the possibility of an easy code injection vulnerability.</p> <div class=highlight><pre><span></span><code>$ var=&#39;-vx[$(echo hi &gt;&amp;2)]&#39;; printf &quot;$var&quot; hi; declare -p x
hi
declare -a x=&#39;([0]=&quot;hi&quot;)&#39;
</code></pre></div> <p>...where the echo can of course be replaced with any arbitrary command. If you must, either specify a hard-coded format string or use -- to signal the end of options. The exact same issue also applies to <a href=../read/ >read</a>, and a similar one to <a href=../mapfile/ >mapfile</a>, though performing expansions into their arguments is less common.</p> </div> <h3 id=arguments>Arguments<a class=headerlink href=#arguments title="Permanent link">&para;</a></h3> <p>Of course in shell-meaning the arguments are just strings, however, the common C-notations plus some additions for number-constants are recognized to give a number-argument to <code>printf</code>:</p> <table> <thead> <tr> <th>Number-Format</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td><code>N</code></td> <td>A normal decimal number</td> </tr> <tr> <td><code>0N</code></td> <td>An octal number</td> </tr> <tr> <td><code>0xN</code></td> <td>A hexadecimal number</td> </tr> <tr> <td><code>0XN</code></td> <td>A hexadecimal number</td> </tr> <tr> <td><code>"X</code></td> <td>(a literal double-quote infront of a character): interpreted as number (underlying codeset) <strong>don't forget escaping</strong></td> </tr> <tr> <td><code>'X</code></td> <td>(a literal single-quote infront of a character): interpreted as number (underlying codeset) <strong>don't forget escaping</strong></td> </tr> </tbody> </table> <p><u><strong>If more arguments than format specifiers</strong></u> are present, then the format string is re-used until the last argument is interpreted. If fewer format specifiers than arguments are present, then number-formats are set to zero, while string-formats are set to null (empty).</p> <p>Take care to avoid <a href=../../../syntax/expansion/wordsplit/ >word splitting</a>, as accidentally passing the wrong number of arguments can produce wildly different and unexpected results. See <a href=../../../syntax/words/ >this article</a>.</p> <div class="admonition danger"> <p class=admonition-title>Attention</p> <p>When a numerical format expects a number, the internal <code>printf</code>-command will use the common Bash arithmetic rules regarding the base. A command like the following example <strong>will</strong> throw an error, since <code>08</code> is not a valid octal number (<code>00</code> to <code>07</code>!):</p> <div class=highlight><pre><span></span><code>printf &#39;%d\n&#39; 08
</code></pre></div> </div> <h3 id=format-strings>Format strings<a class=headerlink href=#format-strings title="Permanent link">&para;</a></h3> <p>The format string interpretion is derived from the C <code>printf()</code> function family. Only format specifiers that end in one of the letters <code>diouxXfeEgGaAcs</code> are recognized.</p> <p>To print a literal <code>%</code> (percent-sign), use <code>%%</code> in the format string.</p> <p><u><strong>Again:</strong></u> Every format specifier expects an associated argument provided!</p> <p>These specifiers have different names, depending who you ask. But they all mean the same: A placeholder for data with a specified format:</p> <ul> <li>format placeholder</li> <li>conversion specification</li> <li>formatting token</li> <li>...</li> </ul> <table> <thead> <tr> <th>Format</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td><code>%b</code></td> <td>Print the associated argument while interpreting backslash escapes in there</td> </tr> <tr> <td><code>%q</code></td> <td>Print the associated argument <strong>shell-quoted</strong>, reusable as input</td> </tr> <tr> <td><code>%d</code></td> <td>Print the associated argument as <strong>signed decimal</strong> number</td> </tr> <tr> <td><code>%i</code></td> <td>Same as <code>%d</code></td> </tr> <tr> <td><code>%o</code></td> <td>Print the associated argument as <strong>unsigned octal</strong> number</td> </tr> <tr> <td><code>%u</code></td> <td>Print the associated argument as <strong>unsigned decimal</strong> number</td> </tr> <tr> <td><code>%x</code></td> <td>Print the associated argument as <strong>unsigned hexadecimal</strong> number with lower-case hex-digits (a-f)</td> </tr> <tr> <td><code>%X</code></td> <td>Same as <code>%x</code>, but with upper-case hex-digits (A-F)</td> </tr> <tr> <td><code>%f</code></td> <td>Interpret and print the associated argument as <strong>floating point</strong> number</td> </tr> <tr> <td><code>%e</code></td> <td>Interpret the associated argument as <strong>double</strong>, and print it in <code>&lt;N&gt;±e&lt;N&gt;</code> format</td> </tr> <tr> <td><code>%E</code></td> <td>Same as <code>%e</code>, but with an upper-case <code>E</code> in the printed format</td> </tr> <tr> <td><code>%g</code></td> <td>Interprets the associated argument as <strong>double</strong>, but prints it like <code>%f</code> or <code>%e</code></td> </tr> <tr> <td><code>%G</code></td> <td>Same as <code>%g</code>, but print it like <code>%E</code></td> </tr> <tr> <td><code>%c</code></td> <td>Interprets the associated argument as <strong>char</strong>: only the first character of a given argument is printed</td> </tr> <tr> <td><code>%s</code></td> <td>Interprets the associated argument literally as string</td> </tr> <tr> <td><code>%n</code></td> <td>Assigns the number of characters printed so far to the variable named in the corresponding argument. Can't specify an array index. If the given name is already an array, the value is assigned to the zeroth element.</td> </tr> <tr> <td><code>%a</code></td> <td>Interprets the associated argument as <strong>double</strong>, and prints it in the form of a C99 <a href=http://www.exploringbinary.com/hexadecimal-floating-point-constants/ >hexadecimal floating-point literal</a>.</td> </tr> <tr> <td><code>%A</code></td> <td>Same as <code>%a</code>, but print it like <code>%E</code></td> </tr> <tr> <td><code>%(FORMAT)T</code></td> <td>output the date-time string resulting from using <code>FORMAT</code> as a format string for <code>strftime(3)</code>. The associated argument is the number of seconds since Epoch, or <code>-1</code> (current time) or <code>-2</code> (shell startup time). If no corresponding argument is supplies, the current time is used as default</td> </tr> <tr> <td><code>%%</code></td> <td>No conversion is done. Produces a <code>%</code> (percent sign)</td> </tr> </tbody> </table> <p>Some of the mentioned format specifiers can modify their behaviour by getting a format modifier:</p> <h3 id=modifiers>Modifiers<a class=headerlink href=#modifiers title="Permanent link">&para;</a></h3> <p>To be more flexible in the output of numbers and strings, the <code>printf</code> command allows format modifiers. These are specified <strong>between</strong> the introductory <code>%</code> and the character that specifies the format:</p> <div class=highlight><pre><span></span><code>printf &quot;%50s\n&quot; &quot;This field is 50 characters wide...&quot;
</code></pre></div> <h4 id=field-and-printing-modifiers>Field and printing modifiers<a class=headerlink href=#field-and-printing-modifiers title="Permanent link">&para;</a></h4> <table> <thead> <tr> <th>Field</th> <th>output format</th> </tr> </thead> <tbody> <tr> <td><code>&lt;N&gt;</code></td> <td><strong>Any number</strong>: Specifies a <strong>minimum field width</strong>, if the text to print is shorter, it's padded with spaces, if the text is longer, the field is expanded</td> </tr> <tr> <td><code>.</code></td> <td><strong>The dot</strong>: Together with a field width, the field is <strong>not</strong> expanded when the text is longer, the text is truncated instead. "<code>%.s</code>" is an undocumented equivalent for "<code>%.0s</code>", which will force a field width of zero, effectively hiding the field from output</td> </tr> <tr> <td><code>*</code></td> <td><strong>The asterisk</strong>: the width is given as argument before the string or number. Usage (the "<code>*</code>" corresponds to the "<code>20</code>"): <code>printf "%*s\n" 20 "test string"</code></td> </tr> <tr> <td><code>#</code></td> <td>"Alternative format" for numbers: see table below</td> </tr> <tr> <td><code>-</code></td> <td><strong>Left-bound</strong> text printing in the field (standard is <strong>right-bound</strong>)</td> </tr> <tr> <td><code>0</code></td> <td>Pads numbers with zeros, not spaces</td> </tr> <tr> <td><code>&lt;space&gt;</code></td> <td>Pad a positive number with a space, where a minus (<code>-</code>) is for negative numbers</td> </tr> <tr> <td><code>+</code></td> <td>Prints all numbers <strong>signed</strong> (<code>+</code> for positive, <code>-</code> for negative)</td> </tr> <tr> <td><code>'</code></td> <td>For decimal conversions, the thousands grouping separator is applied to the integer portion of the output according to the current LC_NUMERIC</td> </tr> </tbody> </table> <p><u><strong>The "alternative format" modifier <code>#</code>:</strong></u></p> <table> <thead> <tr> <th>Alternative</th> <th>Format</th> </tr> </thead> <tbody> <tr> <td><code>%#o</code></td> <td>The octal number is printed with a leading zero, unless it's zero itself</td> </tr> <tr> <td><code>%#x</code>, <code>%#X</code></td> <td>The hex number is printed with a leading "<code>0x</code>"/"<code>0X</code>", unless it's zero</td> </tr> <tr> <td><code>%#g</code>, <code>%#G</code></td> <td>The float number is printed with <strong>trailing zeros</strong> until the number of digits for the current precision is reached (usually trailing zeros are not printed)</td> </tr> <tr> <td>all number formats except <code>%d</code>, <code>%o</code>, <code>%x</code>, <code>%X</code></td> <td>Always print a decimal point in the output, even if no digits follow it</td> </tr> </tbody> </table> <h4 id=precision>Precision<a class=headerlink href=#precision title="Permanent link">&para;</a></h4> <p>The precision for a floating- or double-number can be specified by using <code>.&lt;DIGITS&gt;</code>, where <code>&lt;DIGITS&gt;</code> is the number of digits for precision. If <code>&lt;DIGITS&gt;</code> is an asterisk (<code>*</code>), the precision is read from the argument that precedes the number to print, like (prints 4,3000000000):</p> <div class=highlight><pre><span></span><code>printf &quot;%.*f\n&quot; 10 4,3
</code></pre></div> <p>The format <code>.*N</code> to specify the N'th argument for precision does not work in Bash.</p> <p>For strings, the precision specifies the maximum number of characters to print (i.e., the maximum field width). For integers, it specifies the number of digits to print (zero-padding!).</p> <h3 id=escape-codes>Escape codes<a class=headerlink href=#escape-codes title="Permanent link">&para;</a></h3> <p>These are interpreted if used anywhere in the format string, or in an argument corresponding to a <code>%b</code> format.</p> <table> <thead> <tr> <th>Code</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td><code>\\</code></td> <td>Prints the character <code>\</code> (backslash)</td> </tr> <tr> <td><code>\a</code></td> <td>Prints the alert character (ASCII code 7 decimal)</td> </tr> <tr> <td><code>\b</code></td> <td>Prints a backspace</td> </tr> <tr> <td><code>\f</code></td> <td>Prints a form-feed</td> </tr> <tr> <td><code>\n</code></td> <td>Prints a newline</td> </tr> <tr> <td><code>\r</code></td> <td>Prints a carriage-return</td> </tr> <tr> <td><code>\t</code></td> <td>Prints a horizontal tabulator</td> </tr> <tr> <td><code>\v</code></td> <td>Prints a vertical tabulator</td> </tr> <tr> <td><code>\"</code></td> <td>Prints a <code>'</code></td> </tr> <tr> <td><code>\?</code></td> <td>Prints a <code>?</code></td> </tr> <tr> <td><code>&lt;NNN&gt;</code></td> <td>Interprets <code>&lt;NNN&gt;</code> as <strong>octal</strong> number and prints the corresponding character from the character set</td> </tr> <tr> <td><code>\0&lt;NNN&gt;</code></td> <td>same as <code>&lt;NNN&gt;</code></td> </tr> <tr> <td><code>\x&lt;NNN&gt;</code></td> <td>Interprets <code>&lt;NNN&gt;</code> as <strong>hexadecimal</strong> number and prints the corresponding character from the character set (<strong>3 digits</strong>)</td> </tr> <tr> <td><code>\u&lt;NNNN&gt;</code></td> <td>same as <code>\x&lt;NNN&gt;</code>, but <strong>4 digits</strong></td> </tr> <tr> <td><code>\U&lt;NNNNNNNN&gt;</code></td> <td>same as <code>\x&lt;NNN&gt;</code>, but <strong>8 digits</strong></td> </tr> </tbody> </table> <p>The following additional escape and extra rules apply only to arguments associated with a <code>%b</code> format:</p> <table> <thead> <tr> <th>Escape Rule</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td><code>\c</code></td> <td>Terminate output similarly to the <code>\c</code> escape used by <code>echo -e</code>. printf produces no additional output after coming across a <code>\c</code> escape in a <code>%b</code> argument.</td> </tr> </tbody> </table> <ul> <li>Backslashes in the escapes: <code>\'</code>, <code>\"</code>, and <code>\?</code> are not removed.</li> <li>Octal escapes beginning with <code>\0</code> may contain up to four digits. (POSIX specifies up to three).</li> </ul> <p>These are also respects in which <code>%b</code> differs from the escapes used by <a href=../../../syntax/quoting/#ansi_c_like_strings>\$\'...\'</a> style quoting.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <h3 id=snipplets>Snipplets<a class=headerlink href=#snipplets title="Permanent link">&para;</a></h3> <ul> <li>print the decimal representation of a hexadecimal number (preserve the sign)<ul> <li><code>printf "%d\n" 0x41</code></li> <li><code>printf "%d\n" -0x41</code></li> <li><code>printf "%+d\n" 0x41</code></li> </ul> </li> <li>print the octal representation of a decimal number<ul> <li><code>printf "%o\n" 65</code></li> <li><code>printf "%05o\n" 65</code> (5 characters width, padded with zeros)</li> </ul> </li> <li>this prints a 0, since no argument is specified<ul> <li><code>printf "%d\n"</code></li> </ul> </li> <li>print the code number of the character <code>A</code><ul> <li><code>printf "%d\n" \'A</code></li> <li><code>printf "%d\n" "'A"</code></li> </ul> </li> <li>Generate a greeting banner and assign it to the variable <code>GREETER</code><ul> <li><code>printf -v GREETER "Hello %s" "$LOGNAME"</code></li> </ul> </li> <li>Print a text at the end of the line, using <code>tput</code> to get the current line width<ul> <li><code>printf "%*s\n" $(tput cols) "Hello world!"</code></li> </ul> </li> </ul> <h3 id=small-code-table>Small code table<a class=headerlink href=#small-code-table title="Permanent link">&para;</a></h3> <p>This small loop prints all numbers from 0 to 127 in</p> <ul> <li>decimal</li> <li>octal</li> <li>hex</li> </ul> <div class=highlight><pre><span></span><code><a id=__codelineno-0-1 name=__codelineno-0-1 href=#__codelineno-0-1></a><span class=k>for</span><span class=w> </span><span class=o>((</span><span class=nv>x</span><span class=o>=</span><span class=m>0</span><span class=p>;</span><span class=w> </span>x<span class=w> </span>&lt;<span class=o>=</span><span class=w> </span><span class=m>127</span><span class=p>;</span><span class=w> </span>x++<span class=o>))</span><span class=p>;</span><span class=w> </span><span class=k>do</span>
<a id=__codelineno-0-2 name=__codelineno-0-2 href=#__codelineno-0-2></a><span class=w> </span><span class=nb>printf</span><span class=w> </span><span class=s1>&#39;%3d | %04o | 0x%02x\n&#39;</span><span class=w> </span><span class=s2>&quot;</span><span class=nv>$x</span><span class=s2>&quot;</span><span class=w> </span><span class=s2>&quot;</span><span class=nv>$x</span><span class=s2>&quot;</span><span class=w> </span><span class=s2>&quot;</span><span class=nv>$x</span><span class=s2>&quot;</span>
<a id=__codelineno-0-3 name=__codelineno-0-3 href=#__codelineno-0-3></a><span class=k>done</span>
</code></pre></div> <h3 id=ensure-well-formatted-mac-address>Ensure well-formatted MAC address<a class=headerlink href=#ensure-well-formatted-mac-address title="Permanent link">&para;</a></h3> <p>This code here will take a common MAC address and rewrite it into a well-known format (regarding leading zeros or upper/lowercase of the hex digits, ...):</p> <div class=highlight><pre><span></span><code>the_mac=&quot;0:13:ce:7:7a:ad&quot;
# lowercase hex digits
the_mac=&quot;$(printf &quot;%02x:%02x:%02x:%02x:%02x:%02x&quot; 0x${the_mac//:/ 0x})&quot;
# or the uppercase-digits variant
the_mac=&quot;$(printf &quot;%02X:%02X:%02X:%02X:%02X:%02X&quot; 0x${the_mac//:/ 0x})&quot;
</code></pre></div> <h3 id=replacement-echo>Replacement echo<a class=headerlink href=#replacement-echo title="Permanent link">&para;</a></h3> <p>This code was found in Solaris manpage for echo(1).</p> <p>Solaris version of <code>/usr/bin/echo</code> is equivalent to:</p> <div class=highlight><pre><span></span><code>printf &quot;%b\n&quot; &quot;$*&quot;
</code></pre></div> <p>Solaris <code>/usr/ucb/echo</code> is equivalent to:</p> <div class=highlight><pre><span></span><code>if [ &quot;X$1&quot; = &quot;X-n&quot; ]
then
shift
printf &quot;%s&quot; &quot;$*&quot;
else
printf &quot;%s\n&quot; &quot;$*&quot;
fi
</code></pre></div> <h3 id=prargs-implementation>prargs Implementation<a class=headerlink href=#prargs-implementation title="Permanent link">&para;</a></h3> <p>Working off the replacement echo, here is a terse implementation of prargs:</p> <div class=highlight><pre><span></span><code>printf &#39;&quot;%b&quot;\n&#39; &quot;$0&quot; &quot;$@&quot; | nl -v0 -s&quot;: &quot;
</code></pre></div> <h3 id=repeating-a-character-for-example-to-print-a-line>repeating a character (for example to print a line)<a class=headerlink href=#repeating-a-character-for-example-to-print-a-line title="Permanent link">&para;</a></h3> <p>A small trick: Combining printf and parameter expansion to draw a line</p> <div class=highlight><pre><span></span><code>length=40
printf -v line &#39;%*s&#39; &quot;$length&quot;
echo ${line// /-}
</code></pre></div> <p>or:</p> <div class=highlight><pre><span></span><code>length=40
eval printf -v line &#39;%.0s-&#39; {1..$length}
</code></pre></div> <h3 id=replacement-for-some-calls-to-date1>Replacement for some calls to date(1)<a class=headerlink href=#replacement-for-some-calls-to-date1 title="Permanent link">&para;</a></h3> <p>The <code>%(...)T</code> format string is a direct interface to <code>strftime(3)</code>.</p> <div class=highlight><pre><span></span><code>$ printf &#39;This is week %(%U/%Y)T.\n&#39; -1
This is week 52/2010.
</code></pre></div> <p>Please read the manpage of <code>strftime(3)</code> to get more information about the supported formats.</p> <h2 id=differences-from-awk-printf>differences from awk printf<a class=headerlink href=#differences-from-awk-printf title="Permanent link">&para;</a></h2> <p>Awk also derives its <em>printf()</em> function from C, and therefore has similar format specifiers. However, in all versions of awk the space character is used as a string concatenation operator, so it cannot be used as an argument separator. <strong>Arguments to awk printf must be separated by commas.</strong> Some versions of awk do not require printf arguments to be surrounded by parentheses, but you should use them anyway to provide portability.</p> <p>In the following example, the two strings are concatenated by the intervening space so that no argument remains to fill the format.</p> <div class=highlight><pre><span></span><code>$ echo &quot;Foo&quot; | awk &#39;{ printf &quot;%s\n&quot; $1 }&#39;
awk: (FILENAME=- FNR=1) fatal: not enough arguments to satisfy format string
`%s
Foo&#39;
^ ran out for this one
</code></pre></div> <p>Simply replacing the space with a comma and adding parentheses yields correct awk syntax.</p> <div class=highlight><pre><span></span><code>$ echo &quot;Foo&quot; | awk &#39;{ printf( &quot;%s\n&quot;, $1 ) }&#39;
Foo
</code></pre></div> <p>With appropriate metacharacter escaping the bash printf can be called from inside awk (as from perl and other languages that support shell callout) as long as you don't care about program efficiency or readability.</p> <div class=highlight><pre><span></span><code>echo &quot;Foo&quot; | awk &#39;{ system( &quot;printf \&quot;%s\\n \&quot; \&quot;&quot; $1 &quot;\&quot;&quot; ) }&#39;
Foo
</code></pre></div> <h2 id=differences-from-c-and-portability-considerations>Differences from C, and portability considerations<a class=headerlink href=#differences-from-c-and-portability-considerations title="Permanent link">&para;</a></h2> <ul> <li> <p>The a, A, e, E, f, F, g, and G conversions are supported by Bash, but not required by POSIX.</p> </li> <li> <p>There is no wide-character support (wprintf). For instance, if you use <code>%c</code>, you're actually asking for the first byte of the argument. Likewise, the maximum field width modifier (dot) in combination with <code>%s</code> goes by bytes, not characters. This limits some of printf's functionality to working with ascii only. ksh93's <code>printf</code> supports the <code>L</code> modifier with <code>%s</code> and <code>%c</code> (but so far not <code>%S</code> or <code>%C</code>) in order to treat precision as character width, not byte count. zsh appears to adjust itself dynamically based upon <code>LANG</code> and <code>LC_CTYPE</code>. If <code>LC_CTYPE=C</code>, zsh will throw "character not in range" errors, and otherwise supports wide characters automatically if a variable-width encoding is set for the current locale.</p> </li> <li> <p>Bash recognizes and skips over any characters present in the length modifiers specified by POSIX during format string parsing.</p> </li> </ul> <p><div class=highlight><span class=filename>builtins/printf.def</span><pre><span></span><code><a id=__codelineno-1-1 name=__codelineno-1-1 href=#__codelineno-1-1></a><span class=cp>#define LENMODS &quot;hjlLtz&quot;</span>
<a id=__codelineno-1-2 name=__codelineno-1-2 href=#__codelineno-1-2></a><span class=p>...</span>
<a id=__codelineno-1-3 name=__codelineno-1-3 href=#__codelineno-1-3></a><span class=cm>/* skip possible format modifiers */</span>
<a id=__codelineno-1-4 name=__codelineno-1-4 href=#__codelineno-1-4></a><span class=n>modstart</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>fmt</span><span class=p>;</span>
<a id=__codelineno-1-5 name=__codelineno-1-5 href=#__codelineno-1-5></a><span class=k>while</span><span class=w> </span><span class=p>(</span><span class=o>*</span><span class=n>fmt</span><span class=w> </span><span class=o>&amp;&amp;</span><span class=w> </span><span class=n>strchr</span><span class=w> </span><span class=p>(</span><span class=n>LENMODS</span><span class=p>,</span><span class=w> </span><span class=o>*</span><span class=n>fmt</span><span class=p>))</span>
<a id=__codelineno-1-6 name=__codelineno-1-6 href=#__codelineno-1-6></a><span class=n>fmt</span><span class=o>++</span><span class=p>;</span>
</code></pre></div> - mksh has no built-in printf by default (usually). There is an unsupported compile-time option to include a very poor, basically unusable implementation. For the most part you must rely upon the system's <code>/usr/bin/printf</code> or equivalent. The mksh maintainer recommends using <code>print</code>. The development version (post- R40f) adds a new parameter expansion in the form of <code>${name@Q}</code> which fills the role of <code>printf %q</code> -- expanding in a shell-escaped format.</p> <ul> <li>ksh93 optimizes builtins run from within a command substitution and which have no redirections to run in the shell's process. Therefore the <code>printf -v</code> functionality can be closely matched by <code>var=$(printf ...)</code> without a big performance hit.</li> </ul> <div class=highlight><pre><span></span><code><a id=__codelineno-2-1 name=__codelineno-2-1 href=#__codelineno-2-1></a><span class=c1># Illustrates Bash-like behavior. Redefining printf is usually unnecessary / not recommended.</span>
<a id=__codelineno-2-2 name=__codelineno-2-2 href=#__codelineno-2-2></a><span class=k>function</span><span class=w> </span><span class=nb>printf</span><span class=w> </span><span class=o>{</span>
<a id=__codelineno-2-3 name=__codelineno-2-3 href=#__codelineno-2-3></a><span class=w> </span><span class=k>case</span><span class=w> </span><span class=nv>$1</span><span class=w> </span><span class=k>in</span>
<a id=__codelineno-2-4 name=__codelineno-2-4 href=#__codelineno-2-4></a><span class=w> </span>-v<span class=o>)</span>
<a id=__codelineno-2-5 name=__codelineno-2-5 href=#__codelineno-2-5></a><span class=w> </span><span class=nb>shift</span>
<a id=__codelineno-2-6 name=__codelineno-2-6 href=#__codelineno-2-6></a><span class=w> </span>nameref<span class=w> </span><span class=nv>x</span><span class=o>=</span><span class=nv>$1</span>
<a id=__codelineno-2-7 name=__codelineno-2-7 href=#__codelineno-2-7></a><span class=w> </span><span class=nb>shift</span>
<a id=__codelineno-2-8 name=__codelineno-2-8 href=#__codelineno-2-8></a><span class=w> </span><span class=nv>x</span><span class=o>=</span><span class=k>$(</span><span class=nb>command</span><span class=w> </span><span class=nb>printf</span><span class=w> </span><span class=s2>&quot;</span><span class=nv>$@</span><span class=s2>&quot;</span><span class=k>)</span>
<a id=__codelineno-2-9 name=__codelineno-2-9 href=#__codelineno-2-9></a><span class=w> </span><span class=p>;;</span>
<a id=__codelineno-2-10 name=__codelineno-2-10 href=#__codelineno-2-10></a><span class=w> </span>*<span class=o>)</span>
<a id=__codelineno-2-11 name=__codelineno-2-11 href=#__codelineno-2-11></a><span class=w> </span><span class=nb>command</span><span class=w> </span><span class=nb>printf</span><span class=w> </span><span class=s2>&quot;</span><span class=nv>$@</span><span class=s2>&quot;</span>
<a id=__codelineno-2-12 name=__codelineno-2-12 href=#__codelineno-2-12></a><span class=w> </span><span class=k>esac</span>
<a id=__codelineno-2-13 name=__codelineno-2-13 href=#__codelineno-2-13></a><span class=o>}</span>
<a id=__codelineno-2-14 name=__codelineno-2-14 href=#__codelineno-2-14></a><span class=nb>builtin</span><span class=w> </span>cut
<a id=__codelineno-2-15 name=__codelineno-2-15 href=#__codelineno-2-15></a>print<span class=w> </span><span class=nv>$$</span>
<a id=__codelineno-2-16 name=__codelineno-2-16 href=#__codelineno-2-16></a><span class=nb>printf</span><span class=w> </span>-v<span class=w> </span><span class=s1>&#39;foo[2]&#39;</span><span class=w> </span><span class=s1>&#39;%d\n&#39;</span><span class=w> </span><span class=s2>&quot;</span><span class=k>$(</span>cut<span class=w> </span>-d<span class=w> </span><span class=s1>&#39; &#39;</span><span class=w> </span>-f<span class=w> </span><span class=m>1</span><span class=w> </span>/proc/self/stat<span class=k>)</span><span class=s2>&quot;</span>
<a id=__codelineno-2-17 name=__codelineno-2-17 href=#__codelineno-2-17></a><span class=nb>typeset</span><span class=w> </span>-p<span class=w> </span>foo
<a id=__codelineno-2-18 name=__codelineno-2-18 href=#__codelineno-2-18></a><span class=c1># 22461</span>
<a id=__codelineno-2-19 name=__codelineno-2-19 href=#__codelineno-2-19></a><span class=c1># typeset -a foo=([2]=22461)</span>
</code></pre></div> <ul> <li>The optional Bash loadable <code>print</code> may be useful for ksh compatibility and to overcome some of <a href=../echo/ >echo</a>'s portability pitfalls. Bash, ksh93, and zsh's <code>print</code> have an <code>-f</code> option which takes a <code>printf</code> format string and applies it to the remaining arguments. Bash lists the synopsis as: <code>print: print [-Rnprs] [-u unit] [-f format] [arguments]</code>. However, only <code>-Rrnfu</code> are actually functional. Internally, <code>-p</code> is a noop (it doesn't tie in with Bash coprocs at all), and <code>-s</code> only sets a flag but has no effect. <code>-Cev</code> are unimplemented.</li> <li>Assigning to variables: The <code>printf -v</code> way is slightly different to the way using command-substitution. <a href=../../../syntax/expansion/cmdsubst/ >Command substitution</a> removes trailing newlines before substituting the text, <code>printf -v</code> preserves all output.</li> </ul> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li>SUS: <a href=http://pubs.opengroup.org/onlinepubs/9699919799/utilities/printf.html>printf utility</a> and <a href=http://pubs.opengroup.org/onlinepubs/9699919799/functions/printf.html>printf() function</a></li> <li><a href=../../../snipplets/print_horizontal_line/ >Code snip: Print a horizontal line</a> uses some <code>printf</code> examples</li> <li><a href=http://mywiki.wooledge.org/BashFAQ/018>Greg's BashFAQ 18: How can I use numbers with leading zeros in a loop, e.g., 01, 02?</a></li> </ul> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date">November 7, 2024</span> </span> <span class=md-source-file__fact> <span class=md-icon title=Created> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M14.47 15.08 11 13V7h1.5v5.25l3.08 1.83c-.41.28-.79.62-1.11 1m-1.39 4.84c-.36.05-.71.08-1.08.08-4.42 0-8-3.58-8-8s3.58-8 8-8 8 3.58 8 8c0 .37-.03.72-.08 1.08.69.1 1.33.32 1.92.64.1-.56.16-1.13.16-1.72 0-5.5-4.5-10-10-10S2 6.5 2 12s4.47 10 10 10c.59 0 1.16-.06 1.72-.16-.32-.59-.54-1.23-.64-1.92M18 15v3h-3v2h3v3h2v-3h3v-2h-3v-3z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date">November 7, 2024</span> </span> </aside> <h2 id=__comments>Comments</h2> <script src=https://giscus.app/client.js data-repo=flokoe/bash-hackers-wiki data-repo-id=R_kgDOJ3Nr6Q data-category="Giscus Page Comments" data-category-id=DIC_kwDOJ3Nr6c4CXq9t data-mapping=pathname data-strict=1 data-reactions-enabled=1 data-emit-metadata=0 data-input-position=top data-theme=preferred_color_scheme data-lang=en data-loading=lazy crossorigin=anonymous async>
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