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| -rw-r--r-- | src/bash.md | 91 |
1 files changed, 89 insertions, 2 deletions
diff --git a/src/bash.md b/src/bash.md index 0028724..1dd35a8 100644 --- a/src/bash.md +++ b/src/bash.md @@ -17,10 +17,59 @@ ### Parameter ```bash # default param -# if $foo set, then bar=$foo else bar=some_val -bar=${foo:-some_val} +bar=${foo:-some_val} # if $foo set, then bar=$foo else bar=some_val + +# check param set +bar=${foo:?msg} # if $foo set, then bar=$foo else exit and print msg + +# indirect +FOO=foo +BAR=FOO +bar=${!BAR} # deref value of BAR -> bar=$FOO + +# prefix +${foo#prefix} # remove prefix when expanding $foo +# suffix +${foo%suffix} # remove suffix when expanding $foo + +# substitute +${foo/pattern/string} # replace pattern with string when expanding foo +# pattern starts with +# '/' replace all occurences of pattern +# '#' pattern match at beginning +# '%' pattern match at end +``` + +> Note: `prefix`/`suffix`/`pattern` are expanded as [pathnames](#pathname). + +### Pathname + +```bash +* match any string +? match any single char +\\ match backslash +[abc] match any char of 'a' 'b' 'c' +[a-z] match any char between 'a' - 'z' +[^ab] negate, match all not 'a' 'b' +[:class:] match any char in class, available: + alnum,alpha,ascii,blank,cntrl,digit,graph,lower, + print,punct,space,upper,word,xdigit ``` +Wit `extglob` shell option enabled it is possible to have more powerful +patterns. In the following `pattern-list` is one ore more patterns separated +by `|` char. + +```bash +?(pattern-list) matches zero or one occurrence of the given patterns +*(pattern-list) matches zero or more occurrences of the given patterns ++(pattern-list) matches one or more occurrences of the given patterns +@(pattern-list) matches one of the given patterns +!(pattern-list) matches anything except one of the given patterns +``` +> Note: `shopt -s extglob`/`shopt -u extglob` to enable/disable `extglob` +> option. + ## I/O redirection > Note: The trick with bash I/O redirection is to interpret from left-to-right. @@ -49,4 +98,42 @@ command 2>&1 >file 1. duplicate `fd 1` to `fd 2`, effectively redirecting `stderr` to `stdout` 2. redirect `stdout` to `file` +## Completion + +The `complete` builtin is used to interact with the completion system. +```bash +complete # print currently installed completion handler +complete -F <func> <cmd> # install <func> as completion handler for <cmd> +complete -r <cmd> # uninstall completion handler for <cmd> +``` + +Variables available in completion functions: +```bash +# in +$1 # <cmd> +$2 # current word +$3 # privous word + +COMP_WORDS # array with current command line words +COMP_CWORD # index into COMP_WORDS with current cursor position + +# out +COMPREPLY # array with possible completions +``` + +`compgen` builtin is used to generate possible matches for `word` out of possible `option`s. +The syntax is as follows: +```bash +compgen [option] [word] + +# usefule options: + +# -W <list> compare against word-list +compgen -W "foo foobar bar" "f" + +# -d compare against dir names +# -f compare against file names +compgen -d -f "hom" +``` + [dup2]: http://man7.org/linux/man-pages/man2/dup.2.html |