Bash

• https://github.com/dylanaraps/pure-bash-bible

Redirection

# override to FILE
cmd > FILE
# append to FILE
cmd >> FILE

cmd &> FILE

cmd >& FILE

redirect stdout and stderr to FILE

cmd | cmd2

The standard output of cmd is connected via a pipe to the standard input of cmd2.

cmd |& cmd2

cmd's standard error, in addition to its standard output, is connected to cmd2's standard input through the pipe

Standard input

cmd < FILE
cmd <<< "string"

Pipe

CMD_1 | CMD_2

Multiple commands

CMD_1 ; CMD_2 ; CMD_3

Background task

CMD &

Conditional commands

CMD_1 && CMD_2
CMD_1 || CMD_2

Test flags

• -e : True if the file exists (any type: file, directory, etc.)
• -s : True if the file exists and is non-empty
• -f : True if the file exists and is a regular file
• -d : True if the file exists and is a directory
• -r : True if the file exists and is readable
• -w : True if the file exists and is writable
• -x : True if the file exists and is executable
• -L : True if the file exists and is a symbolic link
• -h : True if the file exists and is a symbolic link (same as -L)
• -p : True if the file exists and is a named pipe (FIFO)
• -S : True if the file exists and is a socket
• -b : True if the file exists and is a block device
• -c : True if the file exists and is a character device
• -t : True if the file descriptor is open and refers to a terminal
• -N : True if the file exists and has been modified since it was last read

Shell tricks

!! # last command
 ls # with a trailing space -> not in history

disown -a && exit # leave terminal but don't kill running processes

Basic command completion

_my_cmd(){
    local cur opts
    # Current word being completed
    cur="${COMP_WORDS[COMP_CWORD]}"

    # The words you want to complete
    opts='run copy $(ls)' # or however you want to list them

    # Fill COMPREPLY with matches
    COMPREPLY=( $(compgen -W "${opts}" -- "$cur") )
}

# some completion for my_cmd
if [[ -v BASH_VERSINFO && "$BASH" == */bash ]]; then
    complete -F _my_cmd my_cmd
fi

Bash symlink

To enable physical path (vs logical) of symlinks you can set a bash option

set -o physical
# same as
set -P