Linux shell script check command success

Question

I need to check the command executed is success or not, I have place the below code in test.sh run it, which give the out by listing the content of /home but there is a warning

./test.sh: 3: ./test.sh: [[: not found

What's wrong in below command

#!/bin/sh
ls /home/
if [[ "$?" != 0 ]]; then
echo "Commnad Error"
else
echo "Commnad Success"
fi

There is no need to check the status of the previous command. You can and should do something liike ls /home 2>/dev/null || echo "Command Error". ` — Valentin Bajrami, Dec 05 '16 at 14:12

score 3 · Accepted Answer · answered Dec 05 '16 at 13:58

According to error:

./test.sh: 3: ./test.sh: [[: not found

Your /bin/sh isn't bash and [[ is bash-specific. Use single bracket [ or test command by itself.
And also use -ne for numeric conditionals. != will work in your specific case, but it's bad practice.

score 2 · Answer 2 · answered Dec 05 '16 at 13:47

2

The error is at if [[ "$?" != 0 ]]; then

number comparison is not done using != Instead -ne is supposed to be used.

Read here for numeric comparison

Also, the correct sytax for the status of the last executed command exit code is $? without the quotes.

if [[ $? -ne 0 ]]; then

answered Dec 05 '16 at 13:47

debal

3,704

Thanks, the problem was with syntax error also there was no need of [ twice, I changed the code to if [ $? -ne 0 ]; then and working. – Haris Dec 05 '16 at 13:58
that doesn't work – Wissam Roujoulah Dec 05 '16 at 13:58

score 1 · Answer 3 · answered Dec 05 '16 at 13:58

1

I guess you are using dash to execute the script because the /bin/sh is a link so you can instead using bash like #!/bin/bash then that warning

answered Dec 05 '16 at 13:58

Wissam Roujoulah

3,229

score 0 · Answer 4 · answered Dec 05 '16 at 14:06

0

Dash doesn't have [[, only [. But even with [, there are reasons to prefer if your_command over your_command; if [ $? = 0 ]. (The former is more straightforward, faster, and resilient to failures in set -e mode).

answered Dec 05 '16 at 14:06

Petr Skocik

28,816

Linux shell script check command success

4 Answers4