SC2320.md

Pattern: $? refers to echo/printf

Issue: -

Description

ShellCheck found a $? that always refers to echo or printf.

This most commonly happens when trying to show $? before doing something with it, without realizing that any such action will also overwrite $?.

In the problematic example, echo "Command exited with $?" was intended to show the exit code before acting on it, but the act of showing $? also overwrote it, so the condition is always false. The solution is to assign $? to a variable first, so that it can be used repeatedly.

Example of incorrect code:

mycommand
echo "Command exited with $?"
if [ $? -ne 0 ]
then
  echo "Failed"
fi

Example of correct code:

mycommand
ret=$?
echo "Command exited with $ret"
if [ $ret -ne 0 ]
then
  echo "Failed"
fi

Further Reading

• ShellCheck - SC2320