bash tips and tricks

bash tips.md

Execute but Keep the Current Working Directory

following code changes cwd to ./step1

cd step_1
./build.sh
./test.sh

adding braces gets the code executed w/o affecting the cwd

(cd step_1 && ./build.sh && ./test.sh)

Special stuff

The bash Variable Index, don't expect info, just index.

Informal and meaningful illustration is following

• $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.

Formal and more lengthy illustration is following

Special parameters

The official list.

Special Variables

The official list.

Coloring terminals

Follow this https://chrisyeh96.github.io/2020/03/28/terminal-colors.html

References

• C learning repo.
• GNU docs
• What are the special dollar sign shell variables on StackOverflow.