I have the following unix shell script, in which i have two integer
variables namely a and b.
If a is greater then or equal to b then shell script should exit with returning 0.
Else it should exit with returning 1.
My try:
Script: ConditionTest.sh
#!/bin/sh
a=10
b=20
if [ $a -ge $b ]
then
exit 0
else
exit 1
fi
....
....
....
Running Script:
$ ./ConditionTest.sh
$
Note: I am not getting any return value after executing the file.
The shell puts the exit status of the last command in the variable ?.
You could simply inspect it:
mycommand
echo $?
... or you could use it to do something else depending on its value:
mycommand && echo "ok" || echo "failed"
or alternatively, and slightly more readable:
if mycommand; then
# exit with 0
echo "ok"
else
# exit with non-zero
echo "failed"
if
Your script looks fine; you did everything right.
#!/bin/sh
a=10
b=20
if [ $a -ge $b ]
then
exit 0
else
exit 1
fi
So here's where we run it and check the return value:
$ sh test.sh
$ echo $?
1
$
10 is not greater than or equal to 20.
Another way to test it would be like this:
$ sh test.sh && echo "succeeded" || echo "failed"
failed
As noted in the comments, you should also quote your variables, always:
if [ $a -ge $b ]
Should be:
if [ "$a" -ge "$b" ]
To add to the previous answers, the key idea you should understand is that every program provides a number when exiting. That number is used as a way to report if the command has completed its operation successfully, and if not, what type of error has occurred.
Like mentioned, the exit code of the last command executed can be accessed with $?.
The reason nothing was printed by your script, is that your script returned 1, but the exit code of a command is not printed. (This is analogous to calling a function, you get a return value from the function but it's not printed)
Related
I am implementing a scenario in Unix Bash scripts. I have two scripts ABC.bash and XYZ.bash. There is one condition in ABC.bash when requester does not enter Y or y scripts exit with message and do not work further. ABC.bash working fine when runs alone.Problem arises when I run it from another bash script i.e. XYZ.bash. It does not check for exit condition. Syntax of logic in XYZ.bash.
echo "Calling ABC.bash from XYZ.bash"
ABC.bash $a $b | tee -a $LOGFILE; sleep 2
if [ ${PIPESTATUS[0]} = 0 ]
then
echo "Do some work"
else
echo "Check ABC.bash input"
exit 1
fi
But when ABC.bash $a $b exit with status 2 flow still goes to IF block rather than ELSE.In log I can see message as DEBUGMODE set to 0. I need this DEBUGMODE setting as it is required but want to exit if ABC.bash exit. Ideally it should go to ELSE part as ABC.bash exit with wrong user input.
Additionally I have set up DEBUGMODE option in XYZ.bash script. Like-
if [[ -z "$1" ]]
then
echo " ">> No input so default to 0"
DEBUGMODE=0
else
echo "DEBUGMODE set to $1"
DEBUGMODE=$1
fi
enter code here
The problem is that PIPESTATUS is a volatile variable. That is it will be reset as soon as any other command is executed. You need to remove the call to sleep 2 if you want to inspect the PIPESTATUS.
In your example, PIPESTATUS reflects the status of sleep 2. So replace
ABC.bash $a $b | tee -a $LOGFILE; sleep 2
if [ ${PIPESTATUS[0]} = 0 ]
by
ABC.bash $a $b | tee -a $LOGFILE; pstat=(${PIPESTATUS[#]}); sleep 2
if [ ${pstat[0]} = 0 ]
to save the status.
As best practice, unless the your code has full control over the any variable content, better to quote the variable. This will not prevent logical error (e.g, the extra sleep that modified the PIPESTATUS), but it will avoid accidental injection of code into the script (or unexpected syntax errors)
if [ "${PIPESTATUS[0]}" = 0 ] ; then
I am running club.sh
inside club.sh script i am running below scripts.
test1.sh
test2.sh
test3.sh
my concern is it should run one by one and if test1 fails it will not run test2.sh and if test2.sh fails it willnot run test3.sh
how can we check? can any one suggest any idea it would be very helpful.
Thanks,
Two approaches -
First, you can examine the exit code of each of your inner scripts (test1.sh, test2.sh, ...) and decide whether to continue accordingly -
$? Will return the exit code of the previous command. It will be 0 (zero) if the script exited without an error. Anything that is not 0 can be considered a failure. So you could so something like this -
./test1.sh # execute script
if [[ $? != 0 ]]; then exit; fi # check return value, exit if not 0
Alternatively, you could use the && bash operator which will only execute subsequent commands if the previous one passed -
./test1.sh && ./test2.sh && test3.sh
Only if test1.sh returns an exit code of 0 (zero) will test2.sh execute and the same goes for test3.sh.
The first approach is good if you need to do some logging or cleanup between executing your scripts, but if you are only concerned that the execution should not continue if there was a failure then the && method would be they way I recommend.
Here is a related post dealing with the meaning behind &&
The returned value of the execution of the first command/script is stored in $? so using this value you can check if your command was successfully executed.
Try this:
bash test1.sh
if [ $? -eq 0 ]; then # if script succeeded
bash test2.sh
else
echo "script failed"
fi
If you want to exit your script whenever a command fails, you just add at the beginning of your script set -e.
#!/bin/bash
set -e
echo hello
ls /root/lalala
echo world
Otherwise, you have two options.
The first one is to use &&. For instance:
echo hello && ls /some_inexistant_directory && echo world
The second one is to check the return value after each command:
#!/bin/bash
echo toto
if [ "$?" != "0" ]; then
exit 1
fi
ls /root
if [ "$?" != "0" ]; then
exit 1
fi
echo world
if [ "$?" != "0" ]; then
exit 1
fi
You just have to put the below at the begging of the script:
#!/bin/bash -e
This question already has answers here:
Automatic exit from Bash shell script on error [duplicate]
(8 answers)
Closed 6 years ago.
#Example Script
wget http://file1.com
cd /dir
wget http://file2.com
wget http://file3.com
I want to execute the bash script line by line and test the exit code ($?) of each execution and determine whether to proceed or not:
It basically means I need to add the following script below every line in the original script:
if test $? -eq 0
then
echo "No error"
else
echo "ERROR"
exit
fi
and the original script becomes:
#Example Script
wget http://file1.com
if test $? -eq 0
then
echo "No error"
else
echo "ERROR"
exit
fi
cd /dir
if test $? -eq 0
then
echo "No error"
else
echo "ERROR"
exit
fi
wget http://file2.com
if test $? -eq 0
then
echo "No error"
else
echo "ERROR"
exit
fi
wget http://file3.com
if test $? -eq 0
then
echo "No error"
else
echo "ERROR"
exit
fi
But the script becomes bloated.
Is there a better method?
One can use set -e but it's not without it's own pitfalls. Alternative one can bail out on errors:
command || exit 1
And an your if-statement can be written less verbose:
if command; then
The above is the same as:
command
if test "$?" -eq 0; then
set -e makes the script fail on non-zero exit status of any command. set +e removes the setting.
There are many ways to do that.
For example can use set in order to automatically stop on "bad" rc; simply by putting
set -e
on top of your script. Alternatively, you could write a "check_rc" function; see here for some starting points.
Or, you start with this:
check_error () {
if [ $RET == 0 ]; then
echo "DONE"
echo ""
else
echo "ERROR"
exit 1
fi
}
To be used with:
echo "some example command"
RET=$? ; check_error
As said; many ways to do this.
Best bet is to use set -e to terminate the script as soon as any non-zero return code is observed. Alternatively you can write a function to deal with error traps and call it after every command, this will reduce the if...else part and you can print any message before exiting.
trap errorsRead ERR;
function errorsRead() {
echo "Some none-zero return code observed..";
exit 1;
}
somecommand #command of your need
errorsRead # calling trap handling function
You can do this contraption:
wget http://file1.com || exit 1
This will terminate the script with error code 1 if a command returns a non-zero (failed) result.
I have the following code snippet in my ksh script.
if [ $rc -ne 0 ]; then
print Error...
exit 1
fi
This block executes since I see the printed statement, but after the script, at the shell prompt, when I type echo $?, the output I get is 0.
I think the code is not getting returned from the snippet mentioned.
I have written below code and run in ksh . the output was as expected
ajay#pavilion:~$ cat ajay.ksh
var=1
if [ $var == 1 ]
then
print "Error"
exit 1
fi
output
ajay#pavilion:~$ ksh
$ ./ajay.ksh
Error
$ echo $?
1
$
I have a bash script file to process something.
control.sh :
c_command="echo 'Hello'; echo ', Stack Overflow';exit 9";
$c_command;
stat=$?;
if [ $stat -eq 0 ];then
echo 'Do something....'
elif [ $stat -eq 9 ];then
echo 'The system will be rebooting...';
else
echo "..."
fi
I use the variable $c_command to execute the command, And I get the exit code is 0 not 9.
If I paste it in command line is work perfect, But when I run in script is very bad.
Generally, when I execute "exit" command in script, then the script will be exit.
And I just want the command done not the script and get the exit code from the command executed.
I solved this problem:
I put the code in $c_command to a script file and run it.
c_command="echo 'Hello'; echo ', Stack Overflow';exit 9";
echo "${c_command}" > tmp.sh;
/bin/bash tmp.sh;
stat=$?;
if [ $stat -eq 0 ];then
echo 'Do something....'
elif [ $stat -eq 9 ];then
echo 'The system will be rebooting...';
else
echo "..."
fi
Take a look at what your script actually prints, and that should give you a clue about why the exit status is 0:
$ bash ./control.sh
'Hello'; echo ', Stack Overflow';exit 9
Do something....
After c_command is expanded, the semicolons are not treated as command separators, but as literal characters. As a result, you have a single echo command that exits 0, not a pair of echo commands followed by an exit command.
Instead of storing code in a string, you should use a function:
c_command () {
echo 'Hello'; echo ', Stack Overflow';return 9
}
c_command
stat=$?