To run more that one command simultaneously we can use the & (ampersand) special character. Another use of & is running the commands in the background. In that case though, you should use & once and the end of the command or script. For example:
# [some command or script] &
Using & (ampersand) to run commands simultaneously
In order to run 2 commands simultaneously use the & special character between the 2 or more commands. The syntax is:
# command1 & command2 & command3 ..
For example, if you want to run 3 commands ‘uname -a’, ‘pwd’ and ‘ls’ simultaneously, you can use:
# hostname & pwd & date
The output would be similar to:
# hostname & pwd & date [1] 3253 [2] 3254 /root geeklab Sat Jan 18 05:46:07 UTC 2020 [1]- Done hostname [2]+ Done pwd
When using single &, even when a command fails the next commands is run.
Using && (double ampersand) to run commands simultaneously
In case if you want that the second job/command needs to wait for the first job/command to finish, use the && between the commands. So in that way if any error occurs while the sentence is being executed it will stop. For example:
# hostname && pwd && date
Sample output:
$ hostname && pwd && date geeklab01 /root Sat Jan 18 12:23:34 IST 2020
Lets try using a wrong command and see if the next commands are executed:
$ hostname && wrngcmd && date geeklab01 -bash: wrngcmd: command not found
As shown above the last command “date” was not executed as the command before it was wrong.