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HTML
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</li> <li class=md-tabs__item> <a href=../../howto/calculate-dc/ class=md-tabs__link> Howto </a> </li> <li class=md-tabs__item> <a href=../../internals/shell_options/ class=md-tabs__link> Internals </a> </li> <li class=md-tabs__item> <a href=../../misc/bashphorisms/ class=md-tabs__link> Misc </a> </li> <li class="md-tabs__item md-tabs__item--active"> <a href=../bashbehaviour/ class=md-tabs__link> Scripting </a> </li> <li class=md-tabs__item> <a href=../../snipplets/ class=md-tabs__link> Snipplets </a> </li> <li class=md-tabs__item> <a href=../../syntax/arith_expr/ class=md-tabs__link> Syntax </a> </li> <li class=md-tabs__item> <a href=../../tags/ class=md-tabs__link> Tags </a> </li> </ul> </div> </nav> <main class=md-main data-md-component=main> <div class="md-main__inner md-grid"> <div class="md-sidebar md-sidebar--primary" data-md-component=sidebar data-md-type=navigation> <div class=md-sidebar__scrollwrap> <div class=md-sidebar__inner> <nav class="md-nav md-nav--primary 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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--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_2> <label class=md-nav__link for=__nav_2 id=__nav_2_label tabindex=0> <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=false> <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=../../commands/classictest/ class=md-nav__link> <span class=md-ellipsis> The classic test command </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_2_2> <label class=md-nav__link for=__nav_2_2 id=__nav_2_2_label tabindex=0> <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=false> <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=../../commands/builtin/caller/ class=md-nav__link> <span class=md-ellipsis> The caller builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/cd/ class=md-nav__link> <span class=md-ellipsis> The cd builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/declare/ class=md-nav__link> <span class=md-ellipsis> The declare builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/echo/ class=md-nav__link> <span class=md-ellipsis> The echo builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/eval/ class=md-nav__link> <span class=md-ellipsis> The eval builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/exec/ class=md-nav__link> <span class=md-ellipsis> The exec builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/exit/ class=md-nav__link> <span class=md-ellipsis> The exit builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/export/ class=md-nav__link> <span class=md-ellipsis> The export builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/kill/ class=md-nav__link> <span class=md-ellipsis> The kill builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/let/ class=md-nav__link> <span class=md-ellipsis> The let builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/local/ class=md-nav__link> <span class=md-ellipsis> The local builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/mapfile/ class=md-nav__link> <span class=md-ellipsis> The mapfile builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/printf/ class=md-nav__link> <span class=md-ellipsis> The printf command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/read/ class=md-nav__link> <span class=md-ellipsis> The read builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/readonly/ class=md-nav__link> <span class=md-ellipsis> The readonly builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/return/ class=md-nav__link> <span class=md-ellipsis> The return builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/set/ class=md-nav__link> <span class=md-ellipsis> The set builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/shift/ class=md-nav__link> <span class=md-ellipsis> The shift builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/shopt/ class=md-nav__link> <span class=md-ellipsis> The shopt builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/trap/ class=md-nav__link> <span class=md-ellipsis> The trap builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/unset/ class=md-nav__link> <span class=md-ellipsis> The unset builtin command </span> </a> </li> <li class=md-nav__item> <a href=../../commands/builtin/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--active md-nav__item--section md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_7 checked> <label class=md-nav__link for=__nav_7 id=__nav_7_label tabindex> <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=true> <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=../bashbehaviour/ class=md-nav__link> <span class=md-ellipsis> Bash's behaviour </span> </a> </li> <li class=md-nav__item> <a href=../bashchanges/ class=md-nav__link> <span class=md-ellipsis> Bash changes </span> </a> </li> <li class=md-nav__item> <a href=../basics/ class=md-nav__link> <span class=md-ellipsis> The basics of shell scripting </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> Debugging a script </span> <span class="md-nav__icon md-icon"></span> </label> <a href=./ class="md-nav__link md-nav__link--active"> <span class=md-ellipsis> Debugging a script </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=#use-a-unique-name-for-your-script class=md-nav__link> <span class=md-ellipsis> Use a unique name for your script </span> </a> </li> <li class=md-nav__item> <a href=#read-the-error-messages class=md-nav__link> <span class=md-ellipsis> Read the error messages </span> </a> </li> <li class=md-nav__item> <a href=#use-a-good-editor class=md-nav__link> <span class=md-ellipsis> Use a good editor </span> </a> </li> <li class=md-nav__item> <a href=#write-logfiles class=md-nav__link> <span class=md-ellipsis> Write logfiles </span> </a> </li> <li class=md-nav__item> <a href=#inject-debugging-code class=md-nav__link> <span class=md-ellipsis> Inject debugging code </span> </a> </li> <li class=md-nav__item> <a href=#use-shell-debug-output class=md-nav__link> <span class=md-ellipsis> Use shell debug output </span> </a> <nav class=md-nav aria-label="Use shell debug output"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#simple-example-of-how-to-interpret-xtrace-output class=md-nav__link> <span class=md-ellipsis> Simple example of how to interpret xtrace output </span> </a> </li> <li class=md-nav__item> <a href=#making-xtrace-more-useful class=md-nav__link> <span class=md-ellipsis> Making xtrace more useful </span> </a> <nav class=md-nav aria-label="Making xtrace more useful"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#set-flag-variables-with-descriptive-words class=md-nav__link> <span class=md-ellipsis> Set flag variables with descriptive words </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#debugging-commands-depending-on-a-set-variable class=md-nav__link> <span class=md-ellipsis> Debugging commands depending on a set variable </span> </a> </li> <li class=md-nav__item> <a href=#dry-run-stdin-driven-commands class=md-nav__link> <span class=md-ellipsis> Dry-run STDIN driven commands </span> </a> </li> <li class=md-nav__item> <a href=#common-error-messages class=md-nav__link> <span class=md-ellipsis> Common error messages </span> </a> <nav class=md-nav aria-label="Common error messages"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#unexpected-end-of-file class=md-nav__link> <span class=md-ellipsis> Unexpected end of file </span> </a> </li> <li class=md-nav__item> <a href=#unexpected-end-of-file-while-looking-for-matching class=md-nav__link> <span class=md-ellipsis> Unexpected end of file while looking for matching ... </span> </a> </li> <li class=md-nav__item> <a href=#too-many-arguments class=md-nav__link> <span class=md-ellipsis> Too many arguments </span> </a> </li> <li class=md-nav__item> <a href=#event-not-found class=md-nav__link> <span class=md-ellipsis> !": event not found </span> </a> </li> <li class=md-nav__item> <a href=#syntax-error-near-unexpected-token class=md-nav__link> <span class=md-ellipsis> syntax error near unexpected token `(\' </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#the-crlf-issue class=md-nav__link> <span class=md-ellipsis> The CRLF issue </span> </a> <nav class=md-nav aria-label="The CRLF issue"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#what-is-the-crlf-issue class=md-nav__link> <span class=md-ellipsis> What is the CRLF issue? </span> </a> </li> <li class=md-nav__item> <a href=#how-did-a-cr-end-up-in-my-file class=md-nav__link> <span class=md-ellipsis> How did a CR end up in my file? </span> </a> </li> <li class=md-nav__item> <a href=#why-do-crs-hurt class=md-nav__link> <span class=md-ellipsis> Why do CRs hurt? </span> </a> </li> <li class=md-nav__item> <a href=#how-can-i-find-and-eliminate-them class=md-nav__link> <span class=md-ellipsis> How can I find and eliminate them? </span> </a> </li> </ul> </nav> </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=../newbie_traps/ class=md-nav__link> <span class=md-ellipsis> Beginner Mistakes </span> </a> </li> <li class=md-nav__item> <a href=../nonportable/ class=md-nav__link> <span class=md-ellipsis> Portability talk </span> </a> </li> <li class=md-nav__item> <a href=../obsolete/ class=md-nav__link> <span class=md-ellipsis> Obsolete and deprecated syntax </span> </a> </li> <li class=md-nav__item> <a href=../posparams/ class=md-nav__link> <span class=md-ellipsis> Handling positional parameters </span> </a> </li> <li class=md-nav__item> <a href=../processtree/ class=md-nav__link> <span class=md-ellipsis> Bash and the process tree </span> </a> </li> <li class=md-nav__item> <a href=../style/ class=md-nav__link> <span class=md-ellipsis> Scripting with style </span> </a> </li> <li class=md-nav__item> <a href=../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=#use-a-unique-name-for-your-script class=md-nav__link> <span class=md-ellipsis> Use a unique name for your script </span> </a> </li> <li class=md-nav__item> <a href=#read-the-error-messages class=md-nav__link> <span class=md-ellipsis> Read the error messages </span> </a> </li> <li class=md-nav__item> <a href=#use-a-good-editor class=md-nav__link> <span class=md-ellipsis> Use a good editor </span> </a> </li> <li class=md-nav__item> <a href=#write-logfiles class=md-nav__link> <span class=md-ellipsis> Write logfiles </span> </a> </li> <li class=md-nav__item> <a href=#inject-debugging-code class=md-nav__link> <span class=md-ellipsis> Inject debugging code </span> </a> </li> <li class=md-nav__item> <a href=#use-shell-debug-output class=md-nav__link> <span class=md-ellipsis> Use shell debug output </span> </a> <nav class=md-nav aria-label="Use shell debug output"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#simple-example-of-how-to-interpret-xtrace-output class=md-nav__link> <span class=md-ellipsis> Simple example of how to interpret xtrace output </span> </a> </li> <li class=md-nav__item> <a href=#making-xtrace-more-useful class=md-nav__link> <span class=md-ellipsis> Making xtrace more useful </span> </a> <nav class=md-nav aria-label="Making xtrace more useful"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#set-flag-variables-with-descriptive-words class=md-nav__link> <span class=md-ellipsis> Set flag variables with descriptive words </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#debugging-commands-depending-on-a-set-variable class=md-nav__link> <span class=md-ellipsis> Debugging commands depending on a set variable </span> </a> </li> <li class=md-nav__item> <a href=#dry-run-stdin-driven-commands class=md-nav__link> <span class=md-ellipsis> Dry-run STDIN driven commands </span> </a> </li> <li class=md-nav__item> <a href=#common-error-messages class=md-nav__link> <span class=md-ellipsis> Common error messages </span> </a> <nav class=md-nav aria-label="Common error messages"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#unexpected-end-of-file class=md-nav__link> <span class=md-ellipsis> Unexpected end of file </span> </a> </li> <li class=md-nav__item> <a href=#unexpected-end-of-file-while-looking-for-matching class=md-nav__link> <span class=md-ellipsis> Unexpected end of file while looking for matching ... </span> </a> </li> <li class=md-nav__item> <a href=#too-many-arguments class=md-nav__link> <span class=md-ellipsis> Too many arguments </span> </a> </li> <li class=md-nav__item> <a href=#event-not-found class=md-nav__link> <span class=md-ellipsis> !": event not found </span> </a> </li> <li class=md-nav__item> <a href=#syntax-error-near-unexpected-token class=md-nav__link> <span class=md-ellipsis> syntax error near unexpected token `(\' </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#the-crlf-issue class=md-nav__link> <span class=md-ellipsis> The CRLF issue </span> </a> <nav class=md-nav aria-label="The CRLF issue"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#what-is-the-crlf-issue class=md-nav__link> <span class=md-ellipsis> What is the CRLF issue? </span> </a> </li> <li class=md-nav__item> <a href=#how-did-a-cr-end-up-in-my-file class=md-nav__link> <span class=md-ellipsis> How did a CR end up in my file? </span> </a> </li> <li class=md-nav__item> <a href=#why-do-crs-hurt class=md-nav__link> <span class=md-ellipsis> Why do CRs hurt? </span> </a> </li> <li class=md-nav__item> <a href=#how-can-i-find-and-eliminate-them class=md-nav__link> <span class=md-ellipsis> How can I find and eliminate them? </span> </a> </li> </ul> </nav> </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"> <nav class=md-tags> <a href=../../tags/#bash class=md-tag>bash</a> <a href=../../tags/#shell class=md-tag>shell</a> <a href=../../tags/#scripting class=md-tag>scripting</a> <a href=../../tags/#bug class=md-tag>bug</a> <a href=../../tags/#debug class=md-tag>debug</a> <a href=../../tags/#debugging class=md-tag>debugging</a> </nav> <a href=https://github.com/flokoe/bash-hackers-wiki/edit/main/docs/scripting/debuggingtips.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/scripting/debuggingtips.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=debugging-a-script>Debugging a script<a class=headerlink href=#debugging-a-script title="Permanent link">¶</a></h1> <p>These few lines are not intended as a full-fledged debugging tutorial, but as hints and comments about debugging a Bash script.</p> <h2 id=use-a-unique-name-for-your-script>Use a unique name for your script<a class=headerlink href=#use-a-unique-name-for-your-script title="Permanent link">¶</a></h2> <p>Do <strong>not</strong> name your script <code>test</code>, for example! <em>Why?</em> <code>test</code> is the name of a UNIX®-command, and <u>most likely built into your shell</u> (it's a built-in in Bash) - so you won't be able to run a script with the name <code>test</code> in a normal way.</p> <p><strong>Don't laugh!</strong> This is a classic mistake :-)</p> <h2 id=read-the-error-messages>Read the error messages<a class=headerlink href=#read-the-error-messages title="Permanent link">¶</a></h2> <p>Many people come into IRC and ask something like <em>"Why does my script fail? I get an error!"</em>. And when you ask them what the error message is, they don't even know. Beautiful.</p> <p>Reading and interpreting error messages is 50% of your job as debugger! Error messages actually <strong>mean</strong> something. At the very least, they can give you hints as to where to start debugging. <strong>READ YOUR ERROR MESSAGES!</strong></p> <p>You may ask yourself why is this mentioned as debugging tip? Well, <u>you would be surprised how many shell users ignore the text of error messages!</u> When I find some time, I'll paste 2 or 3 IRC log-snips here, just to show you that annoying fact.</p> <h2 id=use-a-good-editor>Use a good editor<a class=headerlink href=#use-a-good-editor title="Permanent link">¶</a></h2> <p>Your choice of editor is a matter of personal preference, but one with <strong>Bash syntax highlighting</strong> is highly recommended! Syntax highlighting helps you see (you guessed it) syntax errors, such as unclosed quotes and braces, typos, etc.</p> <p>From my personal experience, I can suggest <code>vim</code> or <code>GNU emacs</code>.</p> <h2 id=write-logfiles>Write logfiles<a class=headerlink href=#write-logfiles title="Permanent link">¶</a></h2> <p>For more complex scripts, it's useful to write to a log file, or to the system log. Nobody can debug your script without knowing what actually happened and what went wrong.</p> <p>An available syslog interface is <code>logger</code> (<a href=http://unixhelp.ed.ac.uk/CGI/man-cgi?logger+1>online manpage</a>).</p> <h2 id=inject-debugging-code>Inject debugging code<a class=headerlink href=#inject-debugging-code title="Permanent link">¶</a></h2> <p>Insert <strong>echos</strong> everywhere you can, and print to <code>stderr</code>:</p> <div class=highlight><pre><span></span><code>echo "DEBUG: current i=$i" >&2
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</code></pre></div> <p>If you read input from <strong>anywhere</strong>, such as a file or <a href=../../syntax/expansion/cmdsubst/ >command substitution</a>, print the debug output with literal quotes, to see leading and trailing spaces!</p> <div class=highlight><pre><span></span><code>pid=$(< fooservice.pid)
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echo "DEBUG: read from file: pid=\"$pid\"" >&2
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</code></pre></div> <p>Bash's <a href=../../commands/builtin/printf/ >printf</a> command has the <code>%q</code> format, which is handy for verifying whether strings are what they appear to be.</p> <div class=highlight><pre><span></span><code>foo=$(< inputfile)
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printf "DEBUG: foo is |%q|\n" "$foo" >&2
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# exposes whitespace (such as CRs, see below) and non-printing characters
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</code></pre></div> <h2 id=use-shell-debug-output>Use shell debug output<a class=headerlink href=#use-shell-debug-output title="Permanent link">¶</a></h2> <p>There are two useful debug outputs for that task (both are written to <code>stderr</code>):</p> <ul> <li><code>set -v</code> mode (<code>set -o verbose</code>)<ul> <li>print commands to be executed to <code>stderr</code> as if they were read from input (script file or keyboard)</li> <li>print everything <strong>before</strong> any (<a href=../../syntax/expansion/intro/ >substitution and expansion</a>, ...) is applied</li> </ul> </li> <li><code>set -x</code> mode (<code>set -o xtrace</code>)<ul> <li>print everything as if it were executed, after <a href=../../syntax/expansion/intro/ >substitution and expansion</a> is applied</li> <li>indicate the depth-level of the subshell (by default by prefixing a <code>+</code> (plus) sign to the displayed command)</li> <li>indicate the recognized words after <a href=../../syntax/expansion/wordsplit/ >word splitting</a> by marking them like <code>'x y'</code></li> <li>in shell version 4.1, this debug output can be printed to a configurable file descriptor, rather than sdtout by setting the <a href=../../syntax/shellvars/#BASH_XTRACEFD>BASH_XTRACEFD</a> variable.</li> </ul> </li> </ul> <p><strong><u>Hint:</u></strong> These modes can be entered when calling Bash:</p> <ul> <li>from commandline: <code>bash -vx ./myscript</code></li> <li>from shebang (OS dependant): <code>#!/bin/bash -vx</code></li> </ul> <h3 id=simple-example-of-how-to-interpret-xtrace-output>Simple example of how to interpret xtrace output<a class=headerlink href=#simple-example-of-how-to-interpret-xtrace-output title="Permanent link">¶</a></h3> <p>Here's a simple command (a string comparison using the <a href=../../commands/classictest/ >classic test command</a>) executed while in <code>set -x</code> mode:</p> <div class=highlight><pre><span></span><code>set -x
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foo="bar baz"
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[ $foo = test ]
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</code></pre></div> <p>That fails. Why? Let's see the <code>xtrace</code> output:</p> <div class=highlight><pre><span></span><code>+ '[' bar baz = test ']'
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</code></pre></div> <p>And now you see that it's ("bar" and "baz") recognized as two separate words (which you would have realized if you READ THE ERROR MESSAGES ;) ). Let's check it...</p> <div class=highlight><pre><span></span><code># next try
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[ "$foo" = test ]
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</code></pre></div> <p><code>xtrace</code> now gives</p> <div class=highlight><pre><span></span><code>+ '[' 'bar baz' = test ']'
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^ ^
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word markers!
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</code></pre></div> <h3 id=making-xtrace-more-useful>Making xtrace more useful<a class=headerlink href=#making-xtrace-more-useful title="Permanent link">¶</a></h3> <p>(by AnMaster)</p> <p><code>xtrace</code> output would be more useful if it contained source file and line number. Add this assignment <a href=../../syntax/shellvars/#PS4>PS4</a> at the beginning of your script to enable the inclusion of that information:</p> <div class=highlight><pre><span></span><code>export PS4='+(${BASH_SOURCE}:${LINENO}): ${FUNCNAME[0]:+${FUNCNAME[0]}(): }'
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</code></pre></div> <p><strong>Be sure to use single quotes here!</strong></p> <p>The output would look like this when you trace code <em>outside a function</em>:</p> <div class=highlight><pre><span></span><code>+(somefile.bash:412): echo 'Hello world'
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</code></pre></div> <p>...and like this when you trace code <em>inside a function</em>:</p> <div class=highlight><pre><span></span><code>+(somefile.bash:412): myfunc(): echo 'Hello world'
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</code></pre></div> <p>That helps a lot when the script is long, or when the main script sources many other files.</p> <h4 id=set-flag-variables-with-descriptive-words>Set flag variables with descriptive words<a class=headerlink href=#set-flag-variables-with-descriptive-words title="Permanent link">¶</a></h4> <p>If you test variables that flag the state of options, such as with <code>if [[ -n $option ]];</code>, consider using descriptive words rather than short codes, such as 0, 1, Y, N, because xtrace will show <code>[[ -n word ]]</code> rather than <code>[[ -n 1 ]]</code> when the option is set.</p> <h2 id=debugging-commands-depending-on-a-set-variable>Debugging commands depending on a set variable<a class=headerlink href=#debugging-commands-depending-on-a-set-variable title="Permanent link">¶</a></h2> <p>For general debugging purposes you can also define a function and a variable to use:</p> <div class=highlight><pre><span></span><code>debugme() {
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[[ $script_debug = 1 ]] && "$@" || :
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# be sure to append || : or || true here or use return 0, since the return code
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# of this function should always be 0 to not influence anything else with an unwanted
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# "false" return code (for example the script's exit code if this function is used
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# as the very last command in the script)
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}
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</code></pre></div> <p>This function does nothing when <code>script_debug</code> is unset or empty, but it executes the given parameters as commands when <code>script_debug</code> is set. Use it like this:</p> <div class=highlight><pre><span></span><code>script_debug=1
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# to turn it off, set script_debug=0
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debugme logger "Sorting the database"
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database_sort
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debugme logger "Finished sorting the database, exit code $?"
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</code></pre></div> <p>Of course this can be used to execute something other than echo during debugging:</p> <div class=highlight><pre><span></span><code>debugme set -x
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# ... some code ...
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debugme set +x
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</code></pre></div> <h2 id=dry-run-stdin-driven-commands>Dry-run STDIN driven commands<a class=headerlink href=#dry-run-stdin-driven-commands title="Permanent link">¶</a></h2> <p>Imagine you have a script that runs FTP commands using the standard FTP client:</p> <div class=highlight><pre><span></span><code><a id=__codelineno-0-1 name=__codelineno-0-1 href=#__codelineno-0-1></a>ftp<span class=w> </span>user@host<span class=w> </span><span class=s><<FTP</span>
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<a id=__codelineno-0-2 name=__codelineno-0-2 href=#__codelineno-0-2></a><span class=s>cd /data</span>
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<a id=__codelineno-0-3 name=__codelineno-0-3 href=#__codelineno-0-3></a><span class=s>get current.log</span>
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<a id=__codelineno-0-4 name=__codelineno-0-4 href=#__codelineno-0-4></a><span class=s>dele current.log</span>
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<a id=__codelineno-0-5 name=__codelineno-0-5 href=#__codelineno-0-5></a><span class=s>FTP</span>
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</code></pre></div> <p>A method to dry-run this with debug output is:</p> <div class=highlight><pre><span></span><code><a id=__codelineno-1-1 name=__codelineno-1-1 href=#__codelineno-1-1></a><span class=k>if</span><span class=w> </span><span class=o>[[</span><span class=w> </span><span class=nv>$DRY_RUN</span><span class=w> </span><span class=o>=</span><span class=w> </span>yes<span class=w> </span><span class=o>]]</span><span class=p>;</span><span class=w> </span><span class=k>then</span>
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<a id=__codelineno-1-2 name=__codelineno-1-2 href=#__codelineno-1-2></a><span class=w> </span>sed<span class=w> </span><span class=s1>'s/^/DRY_RUN FTP: /'</span>
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<a id=__codelineno-1-3 name=__codelineno-1-3 href=#__codelineno-1-3></a><span class=k>else</span>
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<a id=__codelineno-1-4 name=__codelineno-1-4 href=#__codelineno-1-4></a><span class=w> </span>ftp<span class=w> </span>user@host
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<a id=__codelineno-1-5 name=__codelineno-1-5 href=#__codelineno-1-5></a><span class=k>fi</span><span class=w> </span><span class=s><<FTP</span>
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<a id=__codelineno-1-6 name=__codelineno-1-6 href=#__codelineno-1-6></a><span class=s>cd /data</span>
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<a id=__codelineno-1-7 name=__codelineno-1-7 href=#__codelineno-1-7></a><span class=s>get current.log</span>
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<a id=__codelineno-1-8 name=__codelineno-1-8 href=#__codelineno-1-8></a><span class=s>dele current.log</span>
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<a id=__codelineno-1-9 name=__codelineno-1-9 href=#__codelineno-1-9></a><span class=s>FTP</span>
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</code></pre></div> <p>This can be wrapped in a shell function for more readable code.</p> <h2 id=common-error-messages>Common error messages<a class=headerlink href=#common-error-messages title="Permanent link">¶</a></h2> <h3 id=unexpected-end-of-file>Unexpected end of file<a class=headerlink href=#unexpected-end-of-file title="Permanent link">¶</a></h3> <div class=highlight><pre><span></span><code>script.sh: line 100: syntax error: unexpected end of file
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</code></pre></div> <p>Usually indicates exactly what it says: An unexpected end of file. It's unexpected because Bash waits for the closing of a <a href=../../syntax/ccmd/intro/ >compound command</a>:</p> <ul> <li>did you close your <code>do</code> with a <code>done</code>?</li> <li>did you close your <code>if</code> with a <code>fi</code>?</li> <li>did you close your <code>case</code> with a <code>esac</code>?</li> <li>did you close your <code>{</code> with a <code>}</code>?</li> <li>did you close your <code>(</code> with a <code>)</code>?</li> </ul> <p><u><strong>Note:</strong></u> It seems that here-documents (tested on versions <code>1.14.7</code>, <code>2.05b</code>, <code>3.1.17</code> and <code>4.0</code>) are correctly terminated when there is an EOF before the end-of-here-document tag (see <a href=../../syntax/redirection/ >redirection</a>). The reason is unknown, but it seems to be deliberate. Bash 4.0 added an extra message for this: <code>warning: here-document at line <N> delimited by end-of-file (wanted `<MARKER>')</code></p> <h3 id=unexpected-end-of-file-while-looking-for-matching>Unexpected end of file while looking for matching ...<a class=headerlink href=#unexpected-end-of-file-while-looking-for-matching title="Permanent link">¶</a></h3> <div class=highlight><pre><span></span><code>script.sh: line 50: unexpected EOF while looking for matching `"'
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script.sh: line 100: syntax error: unexpected end of file
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</code></pre></div> <p>This one indicates the double-quote opened in line 50 does not have a matching closing quote.</p> <p>These <em>unmatched errors</em> occur with:</p> <ul> <li>double-quote pairs</li> <li>single-quote pairs (also <code>$'string'</code>!)</li> <li>missing a closing <code>}</code> with <a href=../../syntax/pe/ >parameter expansion syntax</a></li> </ul> <h3 id=too-many-arguments>Too many arguments<a class=headerlink href=#too-many-arguments title="Permanent link">¶</a></h3> <div class=highlight><pre><span></span><code>bash: test: too many arguments
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</code></pre></div> <p>You most likely forgot to quote a variable expansion somewhere. See the example for <code>xtrace</code> output from above. External commands may display such an error message though in our example, it was the <strong>internal</strong> test-command that yielded the error.</p> <h3 id=event-not-found>!": event not found<a class=headerlink href=#event-not-found title="Permanent link">¶</a></h3> <div class=highlight><pre><span></span><code>$ echo "Hello world!"
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bash: !": event not found
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</code></pre></div> <p>This is not an error per se. It happens in interactive shells, when the C-Shell-styled history expansion ("<code>!searchword</code>") is enabled. This is the default. Disable it like this:</p> <div class=highlight><pre><span></span><code>set +H
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# or
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set +o histexpand
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</code></pre></div> <h3 id=syntax-error-near-unexpected-token>syntax error near unexpected token `(\'<a class=headerlink href=#syntax-error-near-unexpected-token title="Permanent link">¶</a></h3> <p>When this happens during a script <strong>function definition</strong> or on the commandline, e.g.</p> <div class=highlight><pre><span></span><code>$ foo () { echo "Hello world"; }
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bash: syntax error near unexpected token `('
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</code></pre></div> <p>you most likely have an alias defined with the same name as the function (here: <code>foo</code>). Alias expansion happens before the real language interpretion, thus the alias is expanded and makes your function definition invalid.</p> <h2 id=the-crlf-issue>The CRLF issue<a class=headerlink href=#the-crlf-issue title="Permanent link">¶</a></h2> <h3 id=what-is-the-crlf-issue>What is the CRLF issue?<a class=headerlink href=#what-is-the-crlf-issue title="Permanent link">¶</a></h3> <p>There's a big difference in the way that UNIX® and Microsoft® (and possibly others) handle the <strong>line endings</strong> of plain text files. The difference lies in the use of the CR (Carriage Return) and LF (Line Feed) characters.</p> <ul> <li>MSDOS uses: <code>\r\n</code> (ASCII <code>CR</code> #13 <code>^M</code>, ASCII LF #10)</li> <li>UNIX® uses: <code>\n</code> (ASCII <code>LF</code> #10)</li> </ul> <p>Keep in mind your script is a <strong>plain text file</strong>, and the <code>CR</code> character means nothing special to UNIX® - it is treated like any other character. If it's printed to your terminal, a carriage return will effectively place the cursor at the beginning of the <em>current</em> line. This can cause much confusion and many headaches, since lines containing CRs are not what they appear to be when printed. In summary, CRs are a pain.</p> <h3 id=how-did-a-cr-end-up-in-my-file>How did a CR end up in my file?<a class=headerlink href=#how-did-a-cr-end-up-in-my-file title="Permanent link">¶</a></h3> <p>Some possible sources of CRs:</p> <ul> <li>a DOS/Windows text editor</li> <li>a UNIX® text editor that is "too smart" when determining the file content type (and thinks "<em>it's a DOS text file</em>")</li> <li>a direct copy and paste from certain webpages (some pastebins are known for this)</li> </ul> <h3 id=why-do-crs-hurt>Why do CRs hurt?<a class=headerlink href=#why-do-crs-hurt title="Permanent link">¶</a></h3> <p>CRs can be a nuisance in various ways. They are especially bad when present in the shebang/interpreter specified with <code>#!</code> in the very first line of a script. Consider the following script, written with a Windows® text editor (<code>^M</code> is a symbolic representation of the <code>CR</code> carriage return character!):</p> <div class=highlight><pre><span></span><code>#!/bin/bash^M
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^M
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echo "Hello world"^M
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...
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</code></pre></div> <p>Here's what happens because of the <code>#!/bin/bash^M</code> in our shebang:</p> <ul> <li>the file <code>/bin/bash^M</code> doesn't exist (hopefully)</li> <li>So Bash prints an error message which (depending on the terminal, the Bash version, or custom patches!) may or may not expose the problem.</li> <li>the script can't be executed</li> </ul> <p>The error message can vary. If you're lucky, you'll get:</p> <div class=highlight><pre><span></span><code>bash: ./testing.sh: /bin/bash^M: bad interpreter: No such file or directory
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</code></pre></div> <p>which alerts you to the CR. But you may also get the following:</p> <div class=highlight><pre><span></span><code>: bad interpreter: No such file or directory
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</code></pre></div> <p>Why? Because when printed literally, the <code>^M</code> makes the cursor go back to the beginning of the line. The whole error message is <em>printed</em>, but you <em>see</em> only part of it!</p> <div class="admonition warning"> <p class=admonition-title>warning</p> <p>It's easy to imagine the <code>^M</code> is bad in other places too. If you get weird and illogical messages from your script, rule out the possibility that<code>^M</code> is involved. Find and eliminate it!</p> </div> <h3 id=how-can-i-find-and-eliminate-them>How can I find and eliminate them?<a class=headerlink href=#how-can-i-find-and-eliminate-them title="Permanent link">¶</a></h3> <p><strong>To display</strong> CRs (these are only a few examples)</p> <ul> <li>in VI/VIM: <code>:set list</code></li> <li>with <code>cat(1)</code>: <code>cat -v FILE</code></li> </ul> <p><strong>To eliminate</strong> them (only a few examples)</p> <ul> <li>blindly with <code>tr(1)</code>: <code>tr -d '\r' <FILE >FILE.new</code></li> <li>controlled with <code>recode(1)</code>: <code>recode MSDOS..latin1 FILE</code></li> <li>controlled with <code>dos2unix(1)</code>: <code>dos2unix FILE</code></li> </ul> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li><a href=../../commands/builtin/set/ >the set builtin command</a> (for <code>-v</code> and <code>-x</code>)</li> </ul> <div class="admonition warning"> <p class=admonition-title>FIXME</p> <p>tbd.</p> </div> <ul> <li>DEBUG trap</li> <li>BASH Debugger <a href=http://bashdb.sourceforge.net/ >http://bashdb.sourceforge.net/</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 13, 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 13, 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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