Linuxでbashコマンドのヘルプを表示します。
bashコマンドの一覧を表示する！
helpコマンドを引数なしで実行すると、bashコマンドの一覧が表示されます。「--help」オプションと同じ内容が表示されます。
$ help
GNU bash, version 4.4.19(1)-release (x86_64-redhat-linux-gnu)
These shell commands are defined internally. Type `help' to see this list.
Type `help name' to find out more about the function `name'.
Use `info bash' to find out more about the shell in general.
Use `man -k' or `info' to find out more about commands not in this list.
A star (*) next to a name means that the command is disabled.
job_spec [&] history [-c] [-d offset] [n] or history -anrw [filename]>
(( expression )) if COMMANDS; then COMMANDS; [ elif COMMANDS; then COMMAN>
. filename [arguments] jobs [-lnprs] [jobspec ...] or jobs -x command [args]
: kill [-s sigspec | -n signum | -sigspec] pid | jobspec .>
[ arg... ] let arg [arg ...]
[[ expression ]] local [option] name[=value] ...
alias [-p] [name[=value] ... ] logout [n]
bg [job_spec ...] mapfile [-d delim] [-n count] [-O origin] [-s count] [-t>
bind [-lpsvPSVX] [-m keymap] [-f filename] [-q name] [-u > popd [-n] [+N | -N]
break [n] printf [-v var] format [arguments]
builtin [shell-builtin [arg ...]] pushd [-n] [+N | -N | dir]
caller [expr] pwd [-LP]
case WORD in [PATTERN [| PATTERN]...) COMMANDS ;;]... esa> read [-ers] [-a array] [-d delim] [-i text] [-n nchars] >
cd [-L|[-P [-e]] [-@]] [dir] readarray [-n count] [-O origin] [-s count] [-t] [-u fd]>
command [-pVv] command [arg ...] readonly [-aAf] [name[=value] ...] or readonly -p
compgen [-abcdefgjksuv] [-o option] [-A action] [-G globp> return [n]
complete [-abcdefgjksuv] [-pr] [-DE] [-o option] [-A acti> select NAME [in WORDS ... ;] do COMMANDS; done
compopt [-o|+o option] [-DE] [name ...] set [-abefhkmnptuvxBCHP] [-o option-name] [--] [arg ...]
continue [n] shift [n]
coproc [NAME] command [redirections] shopt [-pqsu] [-o] [optname ...]
declare [-aAfFgilnrtux] [-p] [name[=value] ...] source filename [arguments]
dirs [-clpv] [+N] [-N] suspend [-f]
disown [-h] [-ar] [jobspec ... | pid ...] test [expr]
echo [-neE] [arg ...] time [-p] pipeline
enable [-a] [-dnps] [-f filename] [name ...] times
eval [arg ...] trap [-lp] [[arg] signal_spec ...]
exec [-cl] [-a name] [command [arguments ...]] [redirecti> true
exit [n] type [-afptP] name [name ...]
export [-fn] [name[=value] ...] or export -p typeset [-aAfFgilnrtux] [-p] name[=value] ...
false ulimit [-SHabcdefiklmnpqrstuvxPT] [limit]
fc [-e ename] [-lnr] [first] [last] or fc -s [pat=rep] [c> umask [-p] [-S] [mode]
fg [job_spec] unalias [-a] name [name ...]
for NAME [in WORDS ... ] ; do COMMANDS; done unset [-f] [-v] [-n] [name ...]
for (( exp1; exp2; exp3 )); do COMMANDS; done until COMMANDS; do COMMANDS; done
function name { COMMANDS ; } or name () { COMMANDS ; } variables - Names and meanings of some shell variables
getopts optstring name [arg] wait [-n] [id ...]
hash [-lr] [-p pathname] [-dt] [name ...] while COMMANDS; do COMMANDS; done
help [-dms] [pattern ...] { COMMANDS ; }
コマンドのヘルプを表示する！
コマンド名をオプションに指定して、コマンドのヘルプを表示します。
$ help eval
eval: eval [arg ...]
Execute arguments as a shell command.
Combine ARGs into a single string, use the result as input to the shell,
and execute the resulting commands.
Exit Status:
Returns exit status of command or success if command is null.
$ eval --help
eval: eval [arg ...]
Execute arguments as a shell command.
Combine ARGs into a single string, use the result as input to the shell,
and execute the resulting commands.
Exit Status:
Returns exit status of command or success if command is null.
ヘルプが表示できない場合に使用する！
表示ができないbashの予約語についても、ヘルプを表示することができます。
$ help true
true: true
Return a successful result.
Exit Status:
Always succeeds.
$ true --help
おわりに
コマンドのヘルプは、コマンドのオプションで指定して表示することが多いですが、bashコマンドは、helpコマンドで同じ内容を表示することができます。特に、コマンドのオプションで表示できない場合に使用することができます。
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