How to handle errors in shell script

Question

I am writing shell script to install my application. I have more number of commands in my script such as copy, unzip, move, if and so on. I want to know the error if any of the commands fails. Also I don't want to send exit codes other than zero.

Order of script installation(root-file.sh):-

./script-to-install-mongodb
./script-to-install-jdk8
./script-to-install-myapplicaiton

Sample script file:-

cp sourceDir destinationDir

unzip filename

if [ true] 
// success code
if

I want to know by using variable or any message if any of my scripts command failed in root-file.sh.

I don't want to write code to check every command status. Sometimes cp or mv command may fail due to invalid directory. At the end of script execution, I want to know all commands were executed successfully or error in it?

Is there a way to do it?

Note: I am using shell script not bash

'$?' gives you the status of last command executed, I think you can use that... example - test -x <some file> if [ $? -ne 0 ] then echo "file doesn't exits" exit 0 fi — deepakl
– deepakl, Commented Jul 31, 2017 at 7:51
@karan - please accept answer and vote up, if my solution has solved your problem! — JRG
– JRG, Commented Aug 1, 2017 at 4:00

Uddhav P. Gautam · Accepted Answer · 2017-07-31 08:02:14Z

3

/* the status of your last command stores in special variable $?, you can define variable for $? doing export var=$? */

unzip filename
export unzipStatus=$?
./script1.sh
export script1Status=$?
if [ !["$unzipStatus" || "$script1Status"]]
     then                  
         echo "Everything successful!"       
     else
         echo "unsuccessful"
fi

edited Jul 31, 2017 at 8:02

answered Jul 31, 2017 at 7:52

Uddhav P. Gautam

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2 Comments

Uddhav P. Gautam Over a year ago

@karan, I updated my answer. The logical is if any one status is not successful, the ultimate operation is not successful.

Uddhav P. Gautam Over a year ago

@karan, the logic is simple, you have to negate over all the logical OR.

jagatjyoti · Accepted Answer · 2017-07-31 07:59:47Z

2

Well as you are using shell script to achieve this there's not much external tooling. So the default $? should be of help. You may want to check for retrieval value in between the script. The code will look like this:

./script_1
retval=$?
if $retval==0; then
  echo "script_1 successfully executed ..."
  continue
else; 
  echo "script_1 failed with error exit code !"
  break
fi
./script_2

Lemme know if this added any value to your scenario.

answered Jul 31, 2017 at 7:59

jagatjyoti

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Comments

JRG · Accepted Answer · 2017-07-31 07:58:46Z

1

Exception handling in linux shell scripting can be done as follows

command || fallback_command

If you have multiple commands then you can do

(command_one && command_two) || fallback_command

Here fallback_command can be an echo or log details in a file etc.

I don't know if you have tried putting set -x on top of your script to see detailed execution.

edited Jul 31, 2017 at 7:58

answered Jul 31, 2017 at 7:57

JRG

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1 Comment

JRG Over a year ago

my solution wouldn't need you to check status of each command but will facilitate you to have a fallback command so you can EITHER echo on screen about failure or success OR log details in a log file for later viewing.

sumitya · Accepted Answer · 2017-07-31 10:27:25Z

1

Want to give my 2 cents here. Run your shell like this

sh root-file.sh 2> errors.txt

grep patterns from errors.txt

grep -e "root-file.sh: line" -e "script-to-install-mongodb.sh: line" -e "script-to-install-jdk8.sh: line" -e "script-to-install-myapplicaiton.sh: line" errors.txt

Output of above grep command will display commands which had errors in it along with line no. Let say output is:-

test.sh: line 8: file3: Permission denied

You can just go and check line no.(here it is 8) which had issue. refer this go to line no. in vi.

or this can also be automated: grep specific line from your shell script. grep line with had issue here it is 8.

head -8 test1.sh |tail -1

hope it helps.

answered Jul 31, 2017 at 10:27

sumitya

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