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https://github.com/SixArm/unix-shell-script-tactics

Unix shell script tactics - best practices style guide
https://github.com/SixArm/unix-shell-script-tactics

shell style-guide unix

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Unix shell script tactics - best practices style guide

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# Unix shell script tactics - best practices style guide



This Unix shell script style guide helps us write better Unix shell script code for speed, security, stability, and portability.



This guide is by SixArm.com, a software consultancy. Our customers use shell scripts within a wide variety of Unix shells, so we aim for POSIX for simple scripts.



Highlights:



  * [Aim for POSIX when possible because of portability and standardization](doc/aim-for-posix/)

  * [Protect scripts by using `set` flags such as `set -euf`](doc/protect-scripts-by-using-set-flags/)

  * [Print output with `printf` not `echo`](doc/print-output-with-printf-not-echo/)

  * [Trap signals and exit by using `trap trap_exit EXIT`](doc/trap-signals-and-exit/)

  * [Use a `main()` function](doc/use-a-main-function/)

  * [Run executable with no file name extension](doc/run-executable-with-no-file-name-extension/)

  * [Source with dot operator `.` not keyword `source`](doc/source-with-dot-operator-not-keyword-source/)

  * [Version name: use semantic versioning](doc/version-name-use-semantic-versioning/)

  * [Help: use a function and HERE document](doc/help-use-a-function-and-here-document/)

  * [Date & time format: use UTC and ISO8601](doc/date-time-format-use-utc-and-iso8601/)

  * [Booleans: use true and false](doc/booleans-use-true-and-false/)

  * [Colors: use terminal escape codes & NO_COLOR & TERM=dumb](doc/colors-use-terminal-escape-codes-and-no-color-and-term-dumb/)

  * [Subshells: use parentheses `$()` not backticks](doc/subshells-use-parentheses-not-backticks/)

  * [Trace using set -x then set +x without printing](doc/trace-using-set-x-then-set-x-without-printing/)

  * [Hunt for bugs by using ShellCheck](https://www.shellcheck.net/)

  * [Fix some bugs automatically, if you want, by using Shellharden](https://github.com/anordal/shellharden/)



Recommendations (details of these are TODO):



  * Quote liberally such as `"$var"` instead of just `$var`, for safety.

  * Bulletproof scripts to handle characters such as a quote, newline, leading dash.

  * Enable a user to customize commands by using env vars such as `${FOO:-foo}`.

  * Create temporary files by using `mktemp` instead of `tempfile` et. al.

  

Demo:



  * [Unix shell script tactics demo](bin/unix-shell-script-tactics-demo/)



## Topics



Argument parsing:



  * [for arg do loop](doc/for-arg-do-loop/)

  * [Arg parse](doc/arg-parse/)

  * [Parse options via `while` and `case` not `getopts` or `getopt`](doc/parse-options-via-while-and-case-not-getopts-or-getopt/)



Environment variables:



  * [Test if set or unset](doc/environment-variables/test-if-set-or-unset/)

  * [$FUNCNAME function name](doc/environment-variables/funcname-function-name/)



Directories:



  * [Script directory: use realpath or cd](doc/directories/script-directory-use-realpath-or-cd/)

  * [Log directory: use $LOG_HOME](doc/directories/cache-directory-use-log-home/)

  * [Data directory: use $XDG_DATA_HOME](doc/directories/data-directory-use-xdg-data-home/)

  * [Cache directory: use $XDG_CACHE_HOME](doc/directories/cache-directory-use-xdg-cache-home/)

  * [Configuration directory: use $XDG_CONFIG_HOME](doc/directories/configuration-directory-use-xdg-config-home/)

  * [Runtime directory: use $XDG_RUNTIME_HOME](doc/directories/runtime-directory-use-xdg-runtime-home/)

  * [Temporary directory:: use `mktemp`](doc/directories/temporary-directory-use-mktemp/)



Files:



  * [Temporary file using `mktemp` and `trap`](doc/temporary-file-using-mktemp-and-trap/)

  * [Find files with filter for permission denied](doc/find-files-with-filter-for-permission-denied/)

  * [Find files with special characters](doc/find-files-with-special-characters/)

  * [Find files with readable permissions](doc/find-files-with-readable-permissions/)

  * [Find files with executable, perm, test, exec](doc/find-files-with-executable-perm-test-exec/)



References:



  * [Writing safe shell scripts](https://sipb.mit.edu/doc/safe-shell/)

  * [Rich’s sh (POSIX shell) tricks](http://www.etalabs.net/sh_tricks.html/)

  * [Google Shell Script Style Guide](https://google.github.io/styleguide/shell.xml/)

  * [Filenames and Pathnames in Shell: How to do it Correctly](http://www.dwheeler.com/essays/filenames-in-shell.html/)

  * [Standard Command-Line Options](http://www.tldp.org/LDP/abs/html/standard-options.html/)

  * [How to do things safely in bash](https://github.com/anordal/shellharden/blob/master/how_to_do_things_safely_in_bash.md/)

  * [pure sh bible](https://github.com/dylanaraps/pure-sh-bible) & [pure bash bible](https://github.com/dylanaraps/pure-bash-bible/)



Conventions:



  * [Program name using a string or basename](doc/program-name-using-a-string-or-basename/)

  * [Git top level directory using rev-parse](doc/git-top-level-directory-using-rev-parse/)

  * [Functions: out, err, die, big, log, now, sec, zid, cmd, etc.](doc/functions-out-err-die-big-log-now-sec-zid-cmd-etc/)

  * [Assert functions: assert_empty, assert_equal, assert_match](doc/assert-functions/)

  * [sec() function portability](doc/sec-function-portability/)



Control flow statements:



  * [While loop with index counter](doc/while-loop-with-index-counter/)

  * [Do while loop](doc/do-while-loop/)

  * [Case statement that skips option dash flags](doc/case-statement-that-skips-option-dash-flags/)



Functions:



  * [Export function](doc/export-function/)

  * [Number functions](doc/number-functions/)

  * [Array functions](doc/array-functions/)

  * [URL encode](doc/url-encode/)

  * [URL decode](doc/url-decode/)



Command snippets:



  * [awk match_between](doc/awk-match-between/)



Compatibilities:



  * [`readlink` on macOS behaves differently](doc/readlink-on-macos-behaves-differently/)

  * [`realpath` is` not available on older macOS default](doc/realpath-is-not-available-on-older-macos-default/)



PostgreSQL psql:



  * [psql helpers](doc/psql-helpers/)