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diff --git a/src/bash.md b/src/bash.md deleted file mode 100644 index a4df7da..0000000 --- a/src/bash.md +++ /dev/null @@ -1,169 +0,0 @@ -# bash(1) - -## Expansion - -### Generator - -```bash -# generate sequence from n to m -{n..m} -# generate sequence from n to m step by s -{n..m..s} - -# expand cartesian product -{a,b}{c,d} -``` - -### Parameter -```bash -# default param -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. - -```bash -# stdout & stderr to file -command >file 2>&1 -# equivalent -command &>file - -# stderr to stdout & stdout to file -command 2>&1 >file -``` - -### Explanation - -```bash -j>&i -``` -Duplicate `fd i` to `fd j`, making `j` a copy of `i`. See [dup2(2)][dup2]. - -Example: -```bash -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 -``` - -The `compgen` builtin is used to generate possible matches by comparing `word` -against words generated by `option`. -```bash -compgen [option] [word] - -# usefule options: -# -W <list> specify list of possible completions -# -d generate list with dirs -# -f generate list with files -# -u generate list with users -# -e generate list with exported variables - -# compare "f" against words "foo" "foobar" "bar" and generate matches -compgen -W "foo foobar bar" "f" - -# compare "hom" against file/dir names and generate matches -compgen -d -f "hom" -``` - -### Example -Skeleton to copy/paste for writing simple completions. - -Assume a program `foo` with the following interface: -```bash -foo -c green|red|blue -s low|high -f <file> -h -``` - -The completion handler could be implemented as follows: -```bash -function _foo() { - local curr=$2 - local prev=$3 - - local opts="-c -s -f -h" - case $prev in - -c) COMPREPLY=( $(compgen -W "green red blue" -- $curr) );; - -s) COMPREPLY=( $(compgen -W "low high" -- $curr) );; - -f) COMPREPLY=( $(compgen -f -- $curr) );; - *) COMPREPLY=( $(compgen -W "$opts" -- $curr) );; - esac -} - -complete -F _foo foo -``` - -[dup2]: http://man7.org/linux/man-pages/man2/dup.2.html |