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203 lines
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HTML
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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=./ 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 md-nav--lifted" aria-label=Navigation data-md-level=0> <label 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3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M244.8 8C106.1 8 0 113.3 0 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C428.2 457.8 496 362.9 496 252 496 113.3 383.5 8 244.8 8M97.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 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--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 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> Bash's behaviour </span> <span class="md-nav__icon md-icon"></span> </label> <a href=./ class="md-nav__link md-nav__link--active"> <span class=md-ellipsis> Bash's behaviour </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=#bash-startup-modes class=md-nav__link> <span class=md-ellipsis> Bash startup modes </span> </a> <nav class=md-nav aria-label="Bash startup modes"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#login-shell class=md-nav__link> <span class=md-ellipsis> Login shell </span> </a> </li> <li class=md-nav__item> <a href=#interactive-shell class=md-nav__link> <span class=md-ellipsis> Interactive shell </span> </a> </li> <li class=md-nav__item> <a href=#sh-mode class=md-nav__link> <span class=md-ellipsis> SH mode </span> </a> </li> <li class=md-nav__item> <a href=#posix-mode class=md-nav__link> <span class=md-ellipsis> POSIX mode </span> </a> </li> <li class=md-nav__item> <a href=#quick-startup-file-reference class=md-nav__link> <span class=md-ellipsis> Quick startup file reference </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#bash-run-modes class=md-nav__link> <span class=md-ellipsis> Bash run modes </span> </a> <nav class=md-nav aria-label="Bash run modes"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#normal-bash class=md-nav__link> <span class=md-ellipsis> Normal Bash </span> </a> </li> <li class=md-nav__item> <a href=#posix-run-mode class=md-nav__link> <span class=md-ellipsis> POSIX run mode </span> </a> </li> <li class=md-nav__item> <a href=#restricted-shell class=md-nav__link> <span class=md-ellipsis> Restricted shell </span> </a> </li> </ul> </nav> </li> </ul> </nav> </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> <a href=../debuggingtips/ class=md-nav__link> <span class=md-ellipsis> Debugging a script </span> </a> </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=#bash-startup-modes class=md-nav__link> <span class=md-ellipsis> Bash startup modes </span> </a> <nav class=md-nav aria-label="Bash startup modes"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#login-shell class=md-nav__link> <span class=md-ellipsis> Login shell </span> </a> </li> <li class=md-nav__item> <a href=#interactive-shell class=md-nav__link> <span class=md-ellipsis> Interactive shell </span> </a> </li> <li class=md-nav__item> <a href=#sh-mode class=md-nav__link> <span class=md-ellipsis> SH mode </span> </a> </li> <li class=md-nav__item> <a href=#posix-mode class=md-nav__link> <span class=md-ellipsis> POSIX mode </span> </a> </li> <li class=md-nav__item> <a href=#quick-startup-file-reference class=md-nav__link> <span class=md-ellipsis> Quick startup file reference </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=#bash-run-modes class=md-nav__link> <span class=md-ellipsis> Bash run modes </span> </a> <nav class=md-nav aria-label="Bash run modes"> <ul class=md-nav__list> <li class=md-nav__item> <a href=#normal-bash class=md-nav__link> <span class=md-ellipsis> Normal Bash </span> </a> </li> <li class=md-nav__item> <a href=#posix-run-mode class=md-nav__link> <span class=md-ellipsis> POSIX run mode </span> </a> </li> <li class=md-nav__item> <a href=#restricted-shell class=md-nav__link> <span class=md-ellipsis> Restricted shell </span> </a> </li> </ul> </nav> </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/#startup class=md-tag>startup</a> <a href=../../tags/#files class=md-tag>files</a> <a href=../../tags/#dotfiles class=md-tag>dotfiles</a> <a href=../../tags/#modes class=md-tag>modes</a> <a href=../../tags/#posix class=md-tag>POSIX</a> </nav> <a href=https://github.com/flokoe/bash-hackers-wiki/edit/main/docs/scripting/bashbehaviour.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/bashbehaviour.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=bashs-behaviour>Bash's behaviour<a class=headerlink href=#bashs-behaviour title="Permanent link">¶</a></h1> <div class="admonition warning"> <p class=admonition-title>FIXME</p> <p>incomplete</p> </div> <h2 id=bash-startup-modes>Bash startup modes<a class=headerlink href=#bash-startup-modes title="Permanent link">¶</a></h2> <h3 id=login-shell>Login shell<a class=headerlink href=#login-shell title="Permanent link">¶</a></h3> <p>As a "login shell", Bash reads and sets (executes) the user's profile from <code>/etc/profile</code> and one of <code>~/.bash_profile</code>, <code>~/.bash_login</code>, or <code>~/.profile</code> (in that order, using the first one that's readable!).</p> <p>When a login shell exits, Bash reads and executes commands from the file <code>~/.bash_logout</code>, if it exists.</p> <p>Why an extra login shell mode? There are many actions and variable sets that only make sense for the initial user login. That's why all UNIX® shells have (should have) a "login" mode.</p> <p><u><strong>Methods to start Bash as a login shell:</strong></u></p> <ul> <li>the first character of <code>argv[0]</code> is <code>-</code> (a hyphen): traditional UNIX® shells start from the <code>login</code> binary</li> <li>Bash is started with the <code>-l</code> option</li> <li>Bash is started with the <code>--login</code> option</li> </ul> <p><u><strong>Methods to test for login shell mode:</strong></u></p> <ul> <li>the shell option <code>login_shell</code> is set</li> </ul> <p><u><strong>Related switches:</strong></u></p> <ul> <li><code>--noprofile</code> disables reading of all profile files</li> </ul> <h3 id=interactive-shell>Interactive shell<a class=headerlink href=#interactive-shell title="Permanent link">¶</a></h3> <p>When Bash starts as an interactive non-login shell, it reads and executes commands from <code>~/.bashrc</code>. This file should contain, for example, aliases, since they need to be defined in every shell as they're not inherited from the parent shell.</p> <p>The feature to have a system-wide <code>/etc/bash.bashrc</code> or a similar system-wide rc-file is specific to vendors and distributors that ship <em>their own, patched variant of Bash</em>. The classic way to have a system-wide rc file is to <code>source /etc/bashrc</code> from every user's <code>~/.bashrc</code>.</p> <p><u><strong>Methods to test for interactive-shell mode:</strong></u></p> <ul> <li>the special parameter <code>$-</code> contains the letter <code>i</code> (lowercase I)</li> </ul> <p><u><strong>Related switches:</strong></u></p> <ul> <li><code>-i</code> forces the interactive mode</li> <li><code>--norc</code> disables reading of the startup files (e.g. <code>/etc/bash.bashrc</code> if supported) and <code>~/.bashrc</code></li> <li><code>--rcfile</code> defines another startup file (instead of <code>/etc/bash.bashrc</code> and <code>~/.bashrc</code>)</li> </ul> <h3 id=sh-mode>SH mode<a class=headerlink href=#sh-mode title="Permanent link">¶</a></h3> <p>When Bash starts in SH compatiblity mode, it tries to mimic the startup behaviour of historical versions of <code>sh</code> as closely as possible, while conforming to the POSIX® standard as well. The profile files read are <code>/etc/profile</code> and <code>~/.profile</code>, if it's a login shell.</p> <p>If it's not a login shell, the environment variable <a href=../../syntax/shellvars/#ENV>ENV</a> is evaluated and the resulting filename is used as the name of the startup file.</p> <p>After the startup files are read, Bash enters the <a href=#posix_run_mode>POSIX® compatiblity mode (for running, not for starting!)</a>.</p> <p><u><strong>Bash starts in <code>sh</code> compatiblity mode when:</strong></u></p> <ul> <li>the base filename in <code>argv[0]</code> is <code>sh</code> (:!: NB: <code>/bin/sh</code> may be linked to <code>/bin/bash</code>, but that doesn't mean it acts like <code>/bin/bash</code> :!:)</li> </ul> <h3 id=posix-mode>POSIX mode<a class=headerlink href=#posix-mode title="Permanent link">¶</a></h3> <p>When Bash is started in POSIX® mode, it follows the POSIX® standard for startup files. In this mode, <strong>interactive shells</strong> expand the <a href=../../syntax/shellvars/#ENV>ENV</a> variable and commands are read and executed from the file whose name is the expanded value. No other startup files are read. Hence, a non-interactive shell doesn't read any startup files in POSIX® mode.</p> <p><u><strong>Bash starts in POSIX® mode when:</strong></u></p> <ul> <li>the commandline option <code>--posix</code> is specified</li> <li>the environment variable <a href=../../syntax/shellvars/#POSIXLY_CORRECT>POSIXLY_CORRECT</a> is set</li> </ul> <h3 id=quick-startup-file-reference>Quick startup file reference<a class=headerlink href=#quick-startup-file-reference title="Permanent link">¶</a></h3> <ul> <li>Eventual system-wide rc-files are usually read when <code>~/.bashrc</code> would be read (at least Debian GNU/Linux behaves like that)</li> <li>Regardless of the system-wide files in <code>/etc</code> which are always read, Bash usually reads the first file found, when multiple choices are given (for user files in <code>~/</code>)</li> </ul> <table> <thead> <tr> <th>Mode</th> <th><code>/etc/profile</code></th> <th><code>~/.bash_profile</code></th> <th><code>~/.bash_login</code></th> <th><code>~/.profile</code></th> <th><code>~/.bashrc</code></th> <th><code>${ENV}</code></th> </tr> </thead> <tbody> <tr> <td>Login shell</td> <td>✅</td> <td>✅</td> <td>✅</td> <td>✅</td> <td>🚫</td> <td>🚫</td> </tr> <tr> <td>Interactive shell</td> <td>🚫</td> <td>🚫</td> <td>🚫</td> <td>🚫</td> <td>✅</td> <td>🚫</td> </tr> <tr> <td>SH compatible login</td> <td>✅</td> <td>🚫</td> <td>🚫</td> <td>✅</td> <td>🚫</td> <td>🚫</td> </tr> <tr> <td>SH compatible</td> <td>🚫</td> <td>🚫</td> <td>🚫</td> <td>🚫</td> <td>🚫</td> <td>✅</td> </tr> <tr> <td>POSIX® compatiblity</td> <td>🚫</td> <td>🚫</td> <td>🚫</td> <td>🚫</td> <td>🚫</td> <td>✅</td> </tr> </tbody> </table> <h2 id=bash-run-modes>Bash run modes<a class=headerlink href=#bash-run-modes title="Permanent link">¶</a></h2> <h3 id=normal-bash>Normal Bash<a class=headerlink href=#normal-bash title="Permanent link">¶</a></h3> <h3 id=posix-run-mode>POSIX run mode<a class=headerlink href=#posix-run-mode title="Permanent link">¶</a></h3> <p>In POSIX® mode, Bash follows the POSIX® standard regarding behaviour and parsing (excerpt from a Bash maintainer's document):</p> <div class=highlight><pre><span></span><code>Starting Bash with the `--posix' command-line option or executing `set
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-o posix' while Bash is running will cause Bash to conform more closely
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to the POSIX standard by changing the behavior to match that specified
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by POSIX in areas where the Bash default differs.
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When invoked as `sh', Bash enters POSIX mode after reading the startup
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files.
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The following lists what's changed when Bash is in `POSIX mode':
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1. When a command in the hash table no longer exists, Bash will
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re-search `$PATH' to find the new location. This is also
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available with `shopt -s checkhash'.
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2. The message printed by the job control code and builtins when a job
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exits with a non-zero status is `Done(status)'.
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3. The message printed by the job control code and builtins when a job
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is stopped is `Stopped(SIGNAME)', where SIGNAME is, for example,
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`SIGTSTP'.
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4. The `bg' builtin uses the required format to describe each job
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placed in the background, which does not include an indication of
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whether the job is the current or previous job.
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5. Reserved words appearing in a context where reserved words are
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recognized do not undergo alias expansion.
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6. The POSIX `PS1' and `PS2' expansions of `!' to the history number
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and `!!' to `!' are enabled, and parameter expansion is performed
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on the values of `PS1' and `PS2' regardless of the setting of the
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`promptvars' option.
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7. The POSIX startup files are executed (`$ENV') rather than the
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normal Bash files.
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8. Tilde expansion is only performed on assignments preceding a
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command name, rather than on all assignment statements on the line.
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9. The default history file is `~/.sh_history' (this is the default
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value of `$HISTFILE').
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10. The output of `kill -l' prints all the signal names on a single
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line, separated by spaces, without the `SIG' prefix.
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11. The `kill' builtin does not accept signal names with a `SIG'
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prefix.
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12. Non-interactive shells exit if FILENAME in `.' FILENAME is not
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found.
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13. Non-interactive shells exit if a syntax error in an arithmetic
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expansion results in an invalid expression.
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14. Redirection operators do not perform filename expansion on the word
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in the redirection unless the shell is interactive.
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15. Redirection operators do not perform word splitting on the word in
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the redirection.
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16. Function names must be valid shell names. That is, they may not
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contain characters other than letters, digits, and underscores, and
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may not start with a digit. Declaring a function with an invalid
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name causes a fatal syntax error in non-interactive shells.
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17. POSIX special builtins are found before shell functions during
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command lookup.
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18. If a POSIX special builtin returns an error status, a
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non-interactive shell exits. The fatal errors are those listed in
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the POSIX standard, and include things like passing incorrect
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options, redirection errors, variable assignment errors for
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assignments preceding the command name, etc.
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19. If `CDPATH' is set, the `cd' builtin will not implicitly append
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the current directory to it. This means that `cd' will fail if no
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valid directory name can be constructed from any of the entries in
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`$CDPATH', even if the a directory with the same name as the name
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given as an argument to `cd' exists in the current directory.
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20. A non-interactive shell exits with an error status if a variable
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assignment error occurs when no command name follows the assignment
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statements. A variable assignment error occurs, for example, when
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trying to assign a value to a readonly variable.
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21. A non-interactive shell exits with an error status if the iteration
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variable in a `for' statement or the selection variable in a
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`select' statement is a readonly variable.
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22. Process substitution is not available.
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23. Assignment statements preceding POSIX special builtins persist in
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the shell environment after the builtin completes.
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24. Assignment statements preceding shell function calls persist in the
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shell environment after the function returns, as if a POSIX
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special builtin command had been executed.
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25. The `export' and `readonly' builtin commands display their output
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in the format required by POSIX.
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26. The `trap' builtin displays signal names without the leading `SIG'.
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27. The `trap' builtin doesn't check the first argument for a possible
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signal specification and revert the signal handling to the original
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disposition if it is, unless that argument consists solely of
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digits and is a valid signal number. If users want to reset the
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handler for a given signal to the original disposition, they
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should use `-' as the first argument.
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28. The `.' and `source' builtins do not search the current directory
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for the filename argument if it is not found by searching `PATH'.
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29. Subshells spawned to execute command substitutions inherit the
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value of the `-e' option from the parent shell. When not in POSIX
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mode, Bash clears the `-e' option in such subshells.
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30. Alias expansion is always enabled, even in non-interactive shells.
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31. When the `alias' builtin displays alias definitions, it does not
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display them with a leading `alias ' unless the `-p' option is
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supplied.
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32. When the `set' builtin is invoked without options, it does not
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display shell function names and definitions.
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33. When the `set' builtin is invoked without options, it displays
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variable values without quotes, unless they contain shell
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metacharacters, even if the result contains nonprinting characters.
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34. When the `cd' builtin is invoked in LOGICAL mode, and the pathname
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constructed from `$PWD' and the directory name supplied as an
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argument does not refer to an existing directory, `cd' will fail
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instead of falling back to PHYSICAL mode.
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35. When the `pwd' builtin is supplied the `-P' option, it resets
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`$PWD' to a pathname containing no symlinks.
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36. The `pwd' builtin verifies that the value it prints is the same as
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the current directory, even if it is not asked to check the file
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system with the `-P' option.
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37. When listing the history, the `fc' builtin does not include an
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indication of whether or not a history entry has been modified.
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38. The default editor used by `fc' is `ed'.
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39. The `type' and `command' builtins will not report a non-executable
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file as having been found, though the shell will attempt to
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execute such a file if it is the only so-named file found in
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`$PATH'.
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40. The `vi' editing mode will invoke the `vi' editor directly when
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the `v' command is run, instead of checking `$FCEDIT' and
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`$EDITOR'.
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41. When the `xpg_echo' option is enabled, Bash does not attempt to
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interpret any arguments to `echo' as options. Each argument is
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displayed, after escape characters are converted.
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There is other POSIX behavior that Bash does not implement by default
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even when in POSIX mode. Specifically:
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1. The `fc' builtin checks `$EDITOR' as a program to edit history
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entries if `FCEDIT' is unset, rather than defaulting directly to
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`ed'. `fc' uses `ed' if `EDITOR' is unset.
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2. As noted above, Bash requires the `xpg_echo' option to be enabled
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for the `echo' builtin to be fully conformant.
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Bash can be configured to be POSIX-conformant by default, by specifying
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the `--enable-strict-posix-default' to `configure' when building.
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</code></pre></div> <div class="admonition warning"> <p class=admonition-title>FIXME</p> <p>help me to find out what breaks in POSIX® mode!</p> </div> <p><u><strong>The POSIX® mode can be switched on by:</strong></u></p> <ul> <li>Bash starting as <code>sh</code> (the basename of <code>argv[0]</code> is <code>sh</code>)</li> <li>starting Bash with the commandline option <code>--posix</code></li> <li>on startup, the environment variable <a href=../../syntax/shellvars/#POSIXLY_CORRECT>POSIXLY_CORRECT</a> is set</li> <li>the command <code>set -o posix</code></li> </ul> <p><u><strong>Tests for the POSIX® mode:</strong></u></p> <ul> <li>the variable <a href=../../syntax/shellvars/#SHELLOPTS>SHELLOPTS</a> contains <code>posix</code> in its list</li> </ul> <h3 id=restricted-shell>Restricted shell<a class=headerlink href=#restricted-shell title="Permanent link">¶</a></h3> <p>In restricted mode, Bash sets up (and runs) a shell environment that's far more controlled and limited than the standard shell mode. It acts like normal Bash with the following restrictions:</p> <ul> <li>the <code>cd</code> command can't be used to change directories</li> <li>the variables <a href=../../syntax/shellvars/#SHELL>SHELL</a>, <a href=../../syntax/shellvars/#PATH>PATH</a>, <a href=../../syntax/shellvars/#ENV>ENV</a> and <a href=../../syntax/shellvars/#BASH_ENV>BASH_ENV</a> can't be set or unset</li> <li>command names that contain a <code>/</code> (slash) can't be called (hence you're limited to <code>PATH</code>)</li> <li>filenames containing a <code>/</code> (slash) can't be specified as argument to the <code>source</code> or <code>.</code> builtin command</li> <li>filenames containing a <code>/</code> (slash) can't be specified as argument to the <code>-p</code> option of the <code>hash</code> builtin command</li> <li>function definitions are not inherited from the environment at shell startup</li> <li>the environment variable <a href=../../syntax/shellvars/#SHELLOPTS>SHELLOPTS</a> is ignored at startup</li> <li>redirecting output using the <code>></code>, <code>>|</code>, <code><></code>, <code>>&</code>, <code>&></code>, and <code>>></code> redirection operators isn't allowed</li> <li>the <code>exec</code> builtin command can't replace the shell with another process</li> <li>adding or deleting builtin commands with the <code>-f</code> and <code>-d</code> options to the enable builtin command is forbidden</li> <li>using the <code>enable</code> builtin command to enable disabled shell builtins doesn't work</li> <li>the <code>-p</code> option to the <code>command</code> builtin command doesn't work</li> <li>turning off restricted mode with <code>set +r</code> or <code>set +o restricted</code> is (of course) forbidden</li> </ul> <p>The "-r" restrictions are turned on <strong>after</strong> Bash has read its startup files.</p> <p>When the command that is run is a shell script, then the restrictions are <strong>turned off</strong> for the (sub-)shell that runs that shell script.</p> <p><u><strong>The restricted shell can be switched on by:</strong></u></p> <ul> <li>calling Bash as <code>rbash</code> (the basename of <code>argv[0]</code> is <code>rbash</code>)</li> <li>calling Bash with the <code>-r</code> option</li> <li>calling Bash with the <code>--restricted</code> option</li> </ul> <p><u><strong>Tests for restricted mode:</strong></u></p> <ul> <li>the special parameter <code>$-</code> contains the letter <code>r</code> (lowercase R)</li> <li>the shell option <code>restricted_shell</code> is set and can be checked by the <code>shopt</code> builtin command</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">October 12, 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">October 12, 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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