Command [the shell] return pipe connection determination value

Scenes:

In the command execution bash pipe connections you need to be obtained to the respective command values ​​for determining the return

In the script we may need to print the results to the screen, and saved in a file for later analysis, write the following command

1 command 2》&1 | tee out.txt
2 ST=$?

Found that regardless of whether the value of a successful command, ST is 0, how to solve this problem

 

Solution:

1，set -o pipefail

Set pipefail option, so that when the pipe connection command, the command as long as a pipe connection of any return value is not 0, then the whole expression returns the value is not 0

1 (base) $ ls /root 2> /dev/null | ls /home/ &>/dev/null
2 (base) $ echo $?
3 0
4 (base) $ set -o pipefail 
5 (base) $ ls /root 2> /dev/null | ls /home/ &>/dev/null
6 (base) $ echo $?
7 2

In this way can be used in shells

 

2，$PIPESTATUS

Inside the shell variable, $ PIPESTATUS is an array, the number of pipe connections command, $ PIPESTATUS contains how many values 

1 (base) $ ls /root 2> /dev/null | ls /home/ &>/dev/null
2 (base) $ echo ${PIPESTATUS[@]}
3 2 0

The return command needs to be acquired at the value corresponding to the return value to get

This only take effect in bash, zsh or another shell may be different