downgoon/ioteco

ignore a particular error in bash shell script

downgoon opened this issue · 2 comments

downgoon commented

bash 通常执行到某条语句如果出现错误，则会终止后面语句的运行。但是有时候，我们对一些无关紧要的错误，可以跳过，改怎么办？

实验

  • case A
#!/bin/bash
set -e
echo "before error"
cat /no/path/to/file   # statement-1
echo "after error"

输出：

before error
  • case B
#!/bin/bash
set -e
echo "before error"
cat /no/path/to/file  || true  # statement-2
echo "after error"

输出：

before error
after error

结论

在语句后面加|| true，例如： cat /no/path/to/file || true

解释

Every script you write should include set -e at the top. This tells bash that it should exit the script if any statement returns a non-true return value. The benefit of using -e is that it prevents errors snowballing into serious issues when they could have been caught earlier. Again, for readability you may want to use set -o errexit.

command  
if [ "$?"-ne 0]; then   
    echo "command failed";   
    exit 1;   
fi

等效：

command || { echo "command failed"; exit 1; }

What if you have a command that returns non-zero or you are not interested in its return value? You can use command || true, or if you have a longer section of code, you can turn off the error checking, but I recommend you use this sparingly.

downgoon commented 
set -e # Exit the script if an error happens
set +e # don't bail out of bash script if ccache doesn't exist