Shell script command replacement

Command replacement

When writing a shell script, you may want to use the output result of the `command in the shell script. `` You can use command substitution to ** get the result of a command as a string **.

How to Use

If you write the command you want to execute in parentheses in the format $ (), it will be replaced with the standard output when the shell script is executed.

Example: Display the current date in YYYY-MM-DD format

.sh

$ date '+%Y-%m-%d'
2020-05-04

Used for command replacement

date.sh

#!/bin/bash

filename=$(date '+%Y-%m-%d')
touch "$filename"

Doing this will create a file with the current date in YYYY-MM-DD format.

-rw-rw-r--  1 vagrant vagrant    0 May  4 10:54 2020-05-04

reference

New Linux textbook