- $1, $2, $3, ... are the positional parameters.
"$@" is an array-like construct of all positional parameters, {$1, $2, $3 ...}.
- "$*" is the IFS expansion of all positional parameters, $1 $2 $3 ....
- $# is the number of positional parameters.
- $- current options set for the shell.
- $$ pid of the current shell (not subshell).
- $_ most recent parameter (or the abs path of the command to start the current shell immediately after startup).
- $IFS is the (input) field separator.
- $? is the most recent foreground pipeline exit status.
- $! is the PID of the most recent background command.
- $0 is the name of the shell or shell script.
:
は何もしないコマンド。
- 使いみちは、正常終了させたい時に使う(set -eと併用など)
set -e
はnon zeroなコードが返った場合は終了するので
WAIT_FOR_IT=false
if "${WAIT_FOR_IT}"; then
echo "TRUE!!!"
fi
- https://stackoverflow.com/questions/5163144/what-are-the-special-dollar-sign-shell-variables