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117 lines
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117 lines
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HTML
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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--active md-nav__item--section md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4 checked> <label class=md-nav__link for=__nav_4 id=__nav_4_label tabindex> <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=true> <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 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> Calculating with dc </span> <span class="md-nav__icon md-icon"></span> </label> <a href=./ class="md-nav__link md-nav__link--active"> <span class=md-ellipsis> Calculating with dc </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=#introduction class=md-nav__link> <span class=md-ellipsis> Introduction </span> </a> </li> <li class=md-nav__item> <a href=#simple-calculation class=md-nav__link> <span class=md-ellipsis> Simple calculation </span> </a> </li> <li class=md-nav__item> <a href=#scale-and-base class=md-nav__link> <span class=md-ellipsis> Scale And Base </span> </a> </li> <li class=md-nav__item> <a href=#stack class=md-nav__link> <span class=md-ellipsis> Stack </span> </a> </li> <li class=md-nav__item> <a href=#registers class=md-nav__link> <span class=md-ellipsis> Registers </span> </a> </li> <li class=md-nav__item> <a href=#macros class=md-nav__link> <span class=md-ellipsis> Macros </span> </a> </li> <li class=md-nav__item> <a href=#conditionals-and-loops class=md-nav__link> <span class=md-ellipsis> Conditionals and Loops </span> </a> </li> <li class=md-nav__item> <a href=#next class=md-nav__link> <span class=md-ellipsis> Next </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../collapsing_functions/ class=md-nav__link> <span class=md-ellipsis> Collapsing Functions </span> </a> </li> <li class=md-nav__item> <a href=../conffile/ class=md-nav__link> <span class=md-ellipsis> Config files for your script </span> </a> </li> <li class=md-nav__item> <a href=../dissectabadoneliner/ class=md-nav__link> <span class=md-ellipsis> Dissect a bad oneliner </span> </a> </li> <li class=md-nav__item> <a href=../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=../getopts_tutorial/ class=md-nav__link> <span class=md-ellipsis> Small getopts tutorial </span> </a> </li> <li class=md-nav__item> <a href=../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=../pax/ class=md-nav__link> <span class=md-ellipsis> pax - the POSIX archiver </span> </a> </li> <li class=md-nav__item> <a href=../redirection_tutorial/ class=md-nav__link> <span class=md-ellipsis> Illustrated Redirection Tutorial </span> </a> </li> <li class=md-nav__item> <a href=../testing-your-scripts/ class=md-nav__link> <span class=md-ellipsis> Testing your scripts </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_5> <label class=md-nav__link for=__nav_5 id=__nav_5_label tabindex=0> <span class=md-ellipsis> Internals </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_5_label aria-expanded=false> <label class=md-nav__title for=__nav_5> <span class="md-nav__icon md-icon"></span> Internals </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../internals/shell_options/ class=md-nav__link> <span class=md-ellipsis> List of shell options </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_6> <label class=md-nav__link for=__nav_6 id=__nav_6_label tabindex=0> <span class=md-ellipsis> Misc </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_6_label aria-expanded=false> <label class=md-nav__title for=__nav_6> <span class="md-nav__icon md-icon"></span> Misc </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../misc/bashphorisms/ class=md-nav__link> <span class=md-ellipsis> The Bashphorisms </span> </a> </li> <li class=md-nav__item> <a href=../../misc/readthesourceluke/ class=md-nav__link> <span class=md-ellipsis> Readthesourceluke </span> </a> </li> <li class=md-nav__item> <a href=../../misc/shell_humor/ class=md-nav__link> <span class=md-ellipsis> Shell Humor </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_7> <label class=md-nav__link for=__nav_7 id=__nav_7_label tabindex=0> <span class=md-ellipsis> Scripting </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_7_label aria-expanded=false> <label class=md-nav__title for=__nav_7> <span class="md-nav__icon md-icon"></span> Scripting </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../scripting/bashbehaviour/ class=md-nav__link> <span class=md-ellipsis> Bash's behaviour </span> </a> </li> <li class=md-nav__item> <a href=../../scripting/bashchanges/ class=md-nav__link> <span class=md-ellipsis> Bash changes </span> </a> </li> <li class=md-nav__item> <a href=../../scripting/basics/ class=md-nav__link> <span class=md-ellipsis> The basics of shell scripting </span> </a> </li> <li class=md-nav__item> <a href=../../scripting/debuggingtips/ class=md-nav__link> <span class=md-ellipsis> Debugging a script </span> </a> </li> <li class=md-nav__item> <a href=../../scripting/newbie_traps/ class=md-nav__link> <span class=md-ellipsis> Beginner Mistakes </span> </a> </li> <li class=md-nav__item> <a href=../../scripting/nonportable/ class=md-nav__link> <span class=md-ellipsis> Portability talk </span> </a> </li> <li class=md-nav__item> <a href=../../scripting/obsolete/ class=md-nav__link> <span class=md-ellipsis> Obsolete and deprecated syntax </span> </a> </li> <li class=md-nav__item> <a href=../../scripting/posparams/ class=md-nav__link> <span class=md-ellipsis> Handling positional parameters </span> </a> </li> <li class=md-nav__item> <a href=../../scripting/processtree/ class=md-nav__link> <span class=md-ellipsis> Bash and the process tree </span> </a> </li> <li class=md-nav__item> <a href=../../scripting/style/ class=md-nav__link> <span class=md-ellipsis> Scripting with style </span> </a> </li> <li class=md-nav__item> <a href=../../scripting/terminalcodes/ class=md-nav__link> <span class=md-ellipsis> Terminal codes (ANSI/VT100) introduction </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_8> <label class=md-nav__link for=__nav_8 id=__nav_8_label tabindex=0> <span class=md-ellipsis> Snipplets </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_8_label aria-expanded=false> <label class=md-nav__title for=__nav_8> <span class="md-nav__icon md-icon"></span> Snipplets </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../snipplets/ class=md-nav__link> <span class=md-ellipsis> Small code snipplets </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/add_color_to_your_scripts/ class=md-nav__link> <span class=md-ellipsis> Add Color to your scripts </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/awkcsv/ class=md-nav__link> <span class=md-ellipsis> Using awk to deal with CSV that uses quoted/unquoted delimiters </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/filesize/ class=md-nav__link> <span class=md-ellipsis> Show size of a file </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/kill_bg_job_without_message/ class=md-nav__link> <span class=md-ellipsis> Kill a background job without a message </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/largestfile/ class=md-nav__link> <span class=md-ellipsis> Get largest file </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/pause_command/ class=md-nav__link> <span class=md-ellipsis> Pausing a script (like MSDOS pause command) </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/prargs/ class=md-nav__link> <span class=md-ellipsis> Print argument list for testing </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/print_horizontal_line/ class=md-nav__link> <span class=md-ellipsis> Print a horizontal line </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/rndstr/ class=md-nav__link> <span class=md-ellipsis> Print a random string or select random elements </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/screen_saverestore/ class=md-nav__link> <span class=md-ellipsis> Save and restore terminal/screen content </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/ssh_fetchkeys/ class=md-nav__link> <span class=md-ellipsis> Fetching SSH hostkeys without interaction </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/ssh_local_var/ class=md-nav__link> <span class=md-ellipsis> Run some bash commands with SSH remotely using local variables </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/wrapperargs/ class=md-nav__link> <span class=md-ellipsis> Generate code with own arguments properly quoted </span> </a> </li> <li class=md-nav__item> <a href=../../snipplets/xclip/ class=md-nav__link> <span class=md-ellipsis> X-Clipboard on Commandline </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_9> <label class=md-nav__link for=__nav_9 id=__nav_9_label tabindex=0> <span class=md-ellipsis> Syntax </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_9_label aria-expanded=false> <label class=md-nav__title for=__nav_9> <span class="md-nav__icon md-icon"></span> Syntax </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../syntax/arith_expr/ class=md-nav__link> <span class=md-ellipsis> Arithmetic expressions </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/arrays/ class=md-nav__link> <span class=md-ellipsis> Arrays </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/basicgrammar/ class=md-nav__link> <span class=md-ellipsis> Basic grammar rules of Bash </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/pattern/ class=md-nav__link> <span class=md-ellipsis> Patterns and pattern matching </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/pe/ class=md-nav__link> <span class=md-ellipsis> Parameter expansion </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/quoting/ class=md-nav__link> <span class=md-ellipsis> Quotes and escaping </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/redirection/ class=md-nav__link> <span class=md-ellipsis> Redirection </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/shellvars/ class=md-nav__link> <span class=md-ellipsis> Special parameters and shell variables </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/words/ class=md-nav__link> <span class=md-ellipsis> Words... </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_9_10> <label class=md-nav__link for=__nav_9_10 id=__nav_9_10_label tabindex=0> <span class=md-ellipsis> Ccmd </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_9_10_label aria-expanded=false> <label class=md-nav__title for=__nav_9_10> <span class="md-nav__icon md-icon"></span> Ccmd </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../syntax/ccmd/arithmetic_eval/ class=md-nav__link> <span class=md-ellipsis> Arithmetic evaluation (command) </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/ccmd/c_for/ class=md-nav__link> <span class=md-ellipsis> The C-style for-loop </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/ccmd/case/ class=md-nav__link> <span class=md-ellipsis> The case statement </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/ccmd/classic_for/ class=md-nav__link> <span class=md-ellipsis> The classic for-loop </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/ccmd/conditional_expression/ class=md-nav__link> <span class=md-ellipsis> The conditional expression </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/ccmd/grouping_plain/ class=md-nav__link> <span class=md-ellipsis> Grouping commands </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/ccmd/grouping_subshell/ class=md-nav__link> <span class=md-ellipsis> Grouping commands in a subshell </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/ccmd/if_clause/ class=md-nav__link> <span class=md-ellipsis> The if-clause </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/ccmd/intro/ class=md-nav__link> <span class=md-ellipsis> Bash compound commands </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/ccmd/until_loop/ class=md-nav__link> <span class=md-ellipsis> The until loop </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/ccmd/user_select/ class=md-nav__link> <span class=md-ellipsis> User selections </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/ccmd/while_loop/ class=md-nav__link> <span class=md-ellipsis> The while-loop </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_9_11> <label class=md-nav__link for=__nav_9_11 id=__nav_9_11_label tabindex=0> <span class=md-ellipsis> Expansion </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_9_11_label aria-expanded=false> <label class=md-nav__title for=__nav_9_11> <span class="md-nav__icon md-icon"></span> Expansion </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../syntax/expansion/arith/ class=md-nav__link> <span class=md-ellipsis> Arithmetic expansion </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/expansion/brace/ class=md-nav__link> <span class=md-ellipsis> Brace expansion </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/expansion/cmdsubst/ class=md-nav__link> <span class=md-ellipsis> Command substitution </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/expansion/globs/ class=md-nav__link> <span class=md-ellipsis> Pathname expansion (globbing) </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/expansion/intro/ class=md-nav__link> <span class=md-ellipsis> Expansions and substitutions </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/expansion/proc_subst/ class=md-nav__link> <span class=md-ellipsis> Process substitution </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/expansion/tilde/ class=md-nav__link> <span class=md-ellipsis> Tilde expansion </span> </a> </li> <li class=md-nav__item> <a href=../../syntax/expansion/wordsplit/ class=md-nav__link> <span class=md-ellipsis> Word splitting </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_9_12> <label class=md-nav__link for=__nav_9_12 id=__nav_9_12_label tabindex=0> <span class=md-ellipsis> Grammar </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_9_12_label aria-expanded=false> <label class=md-nav__title for=__nav_9_12> <span class="md-nav__icon md-icon"></span> Grammar </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../syntax/grammar/parser_exec/ class=md-nav__link> <span class=md-ellipsis> Parser exec </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_9_13> <label class=md-nav__link for=__nav_9_13 id=__nav_9_13_label tabindex=0> <span class=md-ellipsis> Keywords </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_9_13_label aria-expanded=false> <label class=md-nav__title for=__nav_9_13> <span class="md-nav__icon md-icon"></span> Keywords </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../syntax/keywords/coproc/ class=md-nav__link> <span class=md-ellipsis> The coproc keyword </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../tags/ class=md-nav__link> <span class=md-ellipsis> Tags </span> </a> </li> </ul> </nav> </div> </div> </div> <div class="md-sidebar md-sidebar--secondary" data-md-component=sidebar data-md-type=toc> <div class=md-sidebar__scrollwrap> <div class=md-sidebar__inner> <nav class="md-nav md-nav--secondary" aria-label="Table of contents"> <label class=md-nav__title for=__toc> <span class="md-nav__icon md-icon"></span> Table of contents </label> <ul class=md-nav__list data-md-component=toc data-md-scrollfix> <li class=md-nav__item> <a href=#introduction class=md-nav__link> <span class=md-ellipsis> Introduction </span> </a> </li> <li class=md-nav__item> <a href=#simple-calculation class=md-nav__link> <span class=md-ellipsis> Simple calculation </span> </a> </li> <li class=md-nav__item> <a href=#scale-and-base class=md-nav__link> <span class=md-ellipsis> Scale And Base </span> </a> </li> <li class=md-nav__item> <a href=#stack class=md-nav__link> <span class=md-ellipsis> Stack </span> </a> </li> <li class=md-nav__item> <a href=#registers class=md-nav__link> <span class=md-ellipsis> Registers </span> </a> </li> <li class=md-nav__item> <a href=#macros class=md-nav__link> <span class=md-ellipsis> Macros </span> </a> </li> <li class=md-nav__item> <a href=#conditionals-and-loops class=md-nav__link> <span class=md-ellipsis> Conditionals and Loops </span> </a> </li> <li class=md-nav__item> <a href=#next class=md-nav__link> <span class=md-ellipsis> Next </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/#arithmetic class=md-tag>arithmetic</a> <a href=../../tags/#calculate class=md-tag>calculate</a> </nav> <a href=https://github.com/flokoe/bash-hackers-wiki/edit/main/docs/howto/calculate-dc.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/howto/calculate-dc.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=calculating-with-dc>Calculating with dc<a class=headerlink href=#calculating-with-dc title="Permanent link">¶</a></h1> <h2 id=introduction>Introduction<a class=headerlink href=#introduction title="Permanent link">¶</a></h2> <p>dc(1) is a non standard, but commonly found, reverse-polish Desk Calculator. According to Ken Thompson, "dc is the oldest language on Unix; it was written on the PDP-7 and ported to the PDP-11 before Unix [itself] was ported".</p> <p>Historically the standard bc(1) has been implemented as a <em>front-end to dc</em>.</p> <h2 id=simple-calculation>Simple calculation<a class=headerlink href=#simple-calculation title="Permanent link">¶</a></h2> <p>In brief, the <em>reverse polish notation</em> means the numbers are put on the stack first, then an operation is applied to them. Instead of writing <code>1+1</code>, you write <code>1 1+</code>.</p> <p>By default <code>dc</code>, unlike <code>bc</code>, doesn't print anything, the result is pushed on the stack. You have to use the "p" command to print the element at the top of the stack. Thus a simple operation looks like:</p> <div class=highlight><pre><span></span><code>$ dc <<< '1 1+pq'
|
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2
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|
</code></pre></div> <p>I used a "here string" present in bash 3.x, ksh93 and zsh. if your shell doesn't support this, you can use <code>echo '1 1+p' | dc</code> or if you have GNU <code>dc</code>, you can use <code>dc -e '1 1 +p'</code>.</p> <p>Of course, you can also just run <code>dc</code> and enter the commands.</p> <p>The classic operations are:</p> <ul> <li>addition: <code>+</code></li> <li>subtraction: <code>-</code></li> <li>division: <code>/</code></li> <li>multiplication: <code>*</code></li> <li>remainder (modulo): <code>%</code></li> <li>exponentiation: <code>^</code></li> <li>square root: <code>v</code></li> </ul> <p>GNU <code>dc</code> adds a couple more.</p> <p>To input a negative number you need to use the <code>_</code> (underscore) character:</p> <div class=highlight><pre><span></span><code>$ dc <<< '1_1-p'
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2
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</code></pre></div> <p>You can use the <em>digits</em> <code>0</code> to <code>9</code> and the <em>letters</em> <code>A</code> to <code>F</code> as numbers, and a dot (<code>.</code>) as a decimal point. The <code>A</code> to <code>F</code> <strong>must</strong> be capital letters in order not to be confused with the commands specified with lower case characters. A number with a letter is considered hexadecimal:</p> <div class=highlight><pre><span></span><code>dc <<< 'Ap'
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10
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</code></pre></div> <p>The <strong>output</strong> is converted to <strong>base 10</strong> by default</p> <h2 id=scale-and-base>Scale And Base<a class=headerlink href=#scale-and-base title="Permanent link">¶</a></h2> <p><code>dc</code> is a calulator with abitrary precision, by default this precision is 0. thus <code>dc <<< "5 4/p"</code> prints "1".</p> <p>We can increase the precision using the <code>k</code> command. It pops the value at the top of the stack and uses it as the precision argument:</p> <div class=highlight><pre><span></span><code>dc <<< '2k5 4/p' # prints 1.25
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dc <<< '4k5 4/p' # prints 1.2500
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dc <<< '100k 2vp'
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1.4142135623730950488016887242096980785696718753769480731766797379907\
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324784621070388503875343276415727
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|
</code></pre></div> <p>dc supports <em>large</em> precision arguments.</p> <p>You can change the base used to output (<em>print</em>) the numbers with <code>o</code> and the base used to input (<em>type</em>) the numbers with <code>i</code>:</p> <div class=highlight><pre><span></span><code>dc << EOF
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20 p# prints 20, output is in base 10
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16o # the output is now in base 2 16
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20p # prints 14, in hex
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16i # the output is now in hex
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p # prints 14 this doesn't modify the number in the stack
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10p # prints 10 the output is done in base 16
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EOF
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</code></pre></div> <p>Note: when the input value is modified, the base is modified for all commands, including <code>i</code>:</p> <div class=highlight><pre><span></span><code>dc << EOF
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|
16i 16o # base is 16 for input and output
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10p # prints 10
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10i # ! set the base to 10 i.e. to 16 decimal
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17p # prints 17
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EOF
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</code></pre></div> <p>This code prints 17 while we might think that <code>10i</code> reverts the base back to 10 and thus the number should be converted to hex and printed as 11. The problem is 10 was typed while the input base 16, thus the base was set to 10 hexadecimal, i.e. 16 decimal.</p> <div class=highlight><pre><span></span><code>dc << EOF
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16o16o10p #prints 10
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Ai # set the base to A in hex i.e. 10
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17p # prints 11 in base 16
|
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EOF
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</code></pre></div> <h2 id=stack>Stack<a class=headerlink href=#stack title="Permanent link">¶</a></h2> <p>There are two basic commands to manipulate the stack:</p> <ul> <li><code>d</code> duplicates the top of the stack</li> <li> <p><code>c</code> clears the stack</p> <p>$ dc << EOF 2 # put 2 on the stack d # duplicate i.e. put another 2 on the stack *p # multiply and print c p # clear and print EOF 4 dc: stack empty</p> </li> </ul> <p><code>c p</code> results in an error, as we would expect, as c removes everything on the stack. <em>Note: we can use <code>#</code> to put comments in the script.</em></p> <p>If you are lost, you can inspect (i.e. print) the stack using the command <code>f</code>. The stack remains unchanged:</p> <div class=highlight><pre><span></span><code>dc <<< '1 2 d 4+f'
|
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6
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|
2
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1
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|
</code></pre></div> <p>Note how the first element that will be popped from the stack is printed first, if you are used to an HP calculator, it's the reverse.</p> <p>Don't hesitate to put <code>f</code> in the examples of this tutorial, it doesn't change the result, and it's a good way to see what's going on.</p> <h2 id=registers>Registers<a class=headerlink href=#registers title="Permanent link">¶</a></h2> <p>The GNU <code>dc</code> manual says that dc has at least <strong>256 registers</strong> depending on the range of unsigned char. I\'m not sure how you are supposed to use the NUL byte. Using a register is easy:</p> <div class=highlight><pre><span></span><code>dc <<EOF
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12 # put 12 on the stack
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sa # remove it from the stack (s), and put it in register 'a'
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10 # put 10 on the stack
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la # read (l) the value of register 'a' and push it on the stack
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+p # add the 2 values and print
|
|
EOF
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|
</code></pre></div> <p>The above snippet uses newlines to embed comments, but it doesn't really matter, you can use <code>echo '12sa10la+p'| dc</code>, with the same results.</p> <p>The register can contain more than just a value, <strong>each register is a stack on its own</strong>.</p> <div class=highlight><pre><span></span><code>dc <<EOF
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12sa #store 12 in 'a'
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6Sa # with a capital S the 6 is removed
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# from the main stack and pushed on the 'a' stack
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lap # prints 6, the value at the top of the 'a' stack
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lap # still prints 6
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Lap # prints 6 also but with a capital L, it pushes the value in 'a'
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# to the main stack and pulls it from the 'a' stack
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lap # prints 12, which is now at the top of the stack
|
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EOF
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|
</code></pre></div> <h2 id=macros>Macros<a class=headerlink href=#macros title="Permanent link">¶</a></h2> <p><code>dc</code> lets you push arbitrary strings on the stack when the strings are enclosed in <code>[]</code>. You can print it with <code>p</code>: <code>dc <<< '[Hello World!]p'</code> and you can evalute it with x: <code>dc <<< '[1 2+]xp'</code>.</p> <p>This is not that interesting until combined with registers. First, let's say we want to calculate the square of a number (don't forget to include <code>f</code> if you get lost!):</p> <div class=highlight><pre><span></span><code>dc << EOF
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3 # push our number on the stack
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d # duplicate it i.e. push 3 on the stack again
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d**p # duplicate again and calculate the product and print
|
|
EOF
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|
</code></pre></div> <p>Now we have several cubes to calculate, we could use <code>dd**</code> several times, or use a macro.</p> <div class=highlight><pre><span></span><code>dc << EOF
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[dd**] # push a string
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sa # save it in register a
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3 # push 3 on the stack
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lax # push the string "dd**" on the stack and execute it
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p # print the result
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4laxp # same operation for 4, in one line
|
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EOF
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|
</code></pre></div> <h2 id=conditionals-and-loops>Conditionals and Loops<a class=headerlink href=#conditionals-and-loops title="Permanent link">¶</a></h2> <p><code>dc</code> can execute a macro stored in a register using the <code>lR x</code> combo, but it can also execute macros conditionally. <code>>a</code> will execute the macro stored in the register <code>a</code>, if the top of the stack is <em>greater than</em> the second element of the stack. Note: the top of the stack contains the last entry. When written, it appears as the reverse of what we are used to reading:</p> <div class=highlight><pre><span></span><code>dc << EOF
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[[Hello World]p] sR # store in 'R' a macro that prints Hello World
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2 1 >R # do nothing 1 is at the top 2 is the second element
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1 2 >R # prints Hello World
|
|
EOF
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|
</code></pre></div> <p>Some <code>dc</code> have <code>>R <R =R</code>, GNU <code>dc</code> had some more, check your manual. Note that the test "consumes" its operands: the 2 first elements are popped off the stack (you can verify that <code>dc <<< "[f]sR 2 1 >R 1 2 >R f"</code> doesn't print anything)</p> <p>Have you noticed how we can <em>include</em> a macro (string) in a macro? and as <code>dc</code> relies on a stack we can, in fact, use the macro recursively (have your favorite control-c key combo ready ;)) :</p> <div class=highlight><pre><span></span><code>dc << EOF
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[ [Hello World] p # our macro starts by printing Hello World
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lRx ] # and then executes the macro in R
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sR # we store it in the register R
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lRx # and finally executes it.
|
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EOF
|
|
</code></pre></div> <p>We have recursivity, we have test, we have loops:</p> <div class=highlight><pre><span></span><code>dc << EOF
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[ li # put our index i on the stack
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p # print it, to see what's going on
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1 - # we decrement the index by one
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si # store decremented index (i=i-1)
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0 li >L # if i > 0 then execute L
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] sL # store our macro with the name L
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|
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10 si # let's give to our index the value 10
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lLx # and start our loop
|
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EOF
|
|
</code></pre></div> <p>Of course code written this way is far too easy to read! Make sure to remove all those extra spaces newlines and comments:</p> <div class=highlight><pre><span></span><code>dc <<< '[lip1-si0li>L]sL10silLx'
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dc <<< '[p1-d0<L]sL10lLx' # use the stack instead of a register
|
|
</code></pre></div> <p>I'll let you figure out the second example, it's not hard, it uses the stack instead of a register for the index.</p> <h2 id=next>Next<a class=headerlink href=#next title="Permanent link">¶</a></h2> <p>Check your dc manual, i haven't decribed everything, like arrays (only documented with "; : are used by bc(1) for array operations" on solaris, probably because <em>echo \'1 0:a 0Sa 2 0:a La 0;ap\' | dc</em> results in //Segmentation Fault (core dump) //, the latest solaris uses GNU dc)</p> <p>You can find more info and dc programs here:</p> <ul> <li><a href=http://en.wikipedia.org/wiki/Dc_(Unix)>http://en.wikipedia.org/wiki/Dc_(Unix)</a></li> </ul> <p>And more example, as well as a dc implementation in python here:</p> <ul> <li><a href=http://en.literateprograms.org/Category:Programming_language:dc>http://en.literateprograms.org/Category:Programming_language:dc</a></li> <li><a href=http://en.literateprograms.org/Desk_calculator_%28Python%29>http://en.literateprograms.org/Desk_calculator_%28Python%29</a></li> </ul> <p>The manual for the 1971 dc from Bell Labs:</p> <ul> <li><a href=http://cm.bell-labs.com/cm/cs/who/dmr/man12.ps>http://cm.bell-labs.com/cm/cs/who/dmr/man12.ps</a> (dead link)</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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