Let's say I have the below command.
STATE_NOT_C_COUNT=`mongo --host "${DB_HOST}" --port 27017 "${MONGO_DATABASE}" --eval "db.$MONGO_DATABASE.count({\"state\" : {"'"$ne"'":\"C\"},\"physicalTableName\":\"table_name\"},{nolock:true})" | tail -1`
When I used to run the above command, got the exception like
exception: connect failed
I want to capture this exception in into the file via the error function.
error(){
if [ "$?" -ne "0" ]; then
echo "$1" 2>&1 error_log
exit 1
fi
}
I'm using the above function like this:
error $STATE_NOT_C_COUNT
But I'm not able to capture the exception through the function in files.
What you are doing is terrible. Let the program that fails print its error messages to stderr, and ensure that stderr is pointed to the right thing. However, the major issue you are having is just lack of quotes. Try:
error "$STATE_NOT_C_COUNT"
The issue is that the command error $STATE_NOT_C_COUNT is subject to field splitting, so if $STATE_NOT_C_COUNT contains any whitespace it is split into arguments, and you are only writing the first one. Another alternative is to write echo "$#" in the function, but this will squash whitespace. However, it cannot be stressed enough that this is a terrible approach, completely against the unix philosophy. The program should write its error to stderr, and you should let them go there. Just make sure stderr is pointed where you want it. The only possible reason to capture stderr is if you want to write it to multiple locations, so you might pipe it to tee or to a syslogger, or some other message bus, but doing such a thing is questionable.
I understand that to check for error level in Linux can be done by using $?. The thing is that the $? value is reset if one of the commands is successfully performed, even if the previous command failed. The code I use for testing as below:
cd /vobs/test2/test3
if [ $2 = "R" ]; then
mv missing ~/missing2
echo "Created"
Assuming that mv missing ~/missing2 failed the $? should be equal to 1 but due to the last command echo "Created" is performed the $? will be equal to 0. How to perform a scan for the code above so that the moment that $?=1 it will execute exit 1 command. I can perform if else for every command execute but it is not the best way to perform, is it? I need some advice on this, please.
You can exit on the first failing command using set -e. This is part of an unofficial "strict bash mode":
set -e
To exit on all errors.
set -o pipefail
To fail on the first issue in a pipeline rather than only last one.
set -u
To fail on access to undefined variables.
I want to raise an error in a Bash script with message "Test cases Failed !!!". How to do this in Bash?
For example:
if [ condition ]; then
raise error "Test cases failed !!!"
fi
This depends on where you want the error message be stored.
You can do the following:
echo "Error!" > logfile.log
exit 125
Or the following:
echo "Error!" 1>&2
exit 64
When you raise an exception you stop the program's execution.
You can also use something like exit xxx where xxx is the error code you may want to return to the operating system (from 0 to 255). Here 125 and 64 are just random codes you can exit with. When you need to indicate to the OS that the program stopped abnormally (eg. an error occurred), you need to pass a non-zero exit code to exit.
As #chepner pointed out, you can do exit 1, which will mean an unspecified error.
Basic error handling
If your test case runner returns a non-zero code for failed tests, you can simply write:
test_handler test_case_x; test_result=$?
if ((test_result != 0)); then
printf '%s\n' "Test case x failed" >&2 # write error message to stderr
exit 1 # or exit $test_result
fi
Or even shorter:
if ! test_handler test_case_x; then
printf '%s\n' "Test case x failed" >&2
exit 1
fi
Or the shortest:
test_handler test_case_x || { printf '%s\n' "Test case x failed" >&2; exit 1; }
To exit with test_handler's exit code:
test_handler test_case_x || { ec=$?; printf '%s\n' "Test case x failed" >&2; exit $ec; }
Advanced error handling
If you want to take a more comprehensive approach, you can have an error handler:
exit_if_error() {
local exit_code=$1
shift
[[ $exit_code ]] && # do nothing if no error code passed
((exit_code != 0)) && { # do nothing if error code is 0
printf 'ERROR: %s\n' "$#" >&2 # we can use better logging here
exit "$exit_code" # we could also check to make sure
# error code is numeric when passed
}
}
then invoke it after running your test case:
run_test_case test_case_x
exit_if_error $? "Test case x failed"
or
run_test_case test_case_x || exit_if_error $? "Test case x failed"
The advantages of having an error handler like exit_if_error are:
we can standardize all the error handling logic such as logging, printing a stack trace, notification, doing cleanup etc., in one place
by making the error handler get the error code as an argument, we can spare the caller from the clutter of if blocks that test exit codes for errors
if we have a signal handler (using trap), we can invoke the error handler from there
Error handling and logging library
Here is a complete implementation of error handling and logging:
https://github.com/codeforester/base/blob/master/lib/stdlib.sh
Related posts
Error handling in Bash
The 'caller' builtin command on Bash Hackers Wiki
Are there any standard exit status codes in Linux?
BashFAQ/105 - Why doesn't set -e (or set -o errexit, or trap ERR) do what I expected?
Equivalent of __FILE__, __LINE__ in Bash
Is there a TRY CATCH command in Bash
To add a stack trace to the error handler, you may want to look at this post: Trace of executed programs called by a Bash script
Ignoring specific errors in a shell script
Catching error codes in a shell pipe
How do I manage log verbosity inside a shell script?
How to log function name and line number in Bash?
Is double square brackets [[ ]] preferable over single square brackets [ ] in Bash?
There are a couple more ways with which you can approach this problem. Assuming one of your requirement is to run a shell script/function containing a few shell commands and check if the script ran successfully and throw errors in case of failures.
The shell commands in generally rely on exit-codes returned to let the shell know if it was successful or failed due to some unexpected events.
So what you want to do falls upon these two categories
exit on error
exit and clean-up on error
Depending on which one you want to do, there are shell options available to use. For the first case, the shell provides an option with set -e and for the second you could do a trap on EXIT
Should I use exit in my script/function?
Using exit generally enhances readability In certain routines, once you know the answer, you want to exit to the calling routine immediately. If the routine is defined in such a way that it doesn’t require any further cleanup once it detects an error, not exiting immediately means that you have to write more code.
So in cases if you need to do clean-up actions on script to make the termination of the script clean, it is preferred to not to use exit.
Should I use set -e for error on exit?
No!
set -e was an attempt to add "automatic error detection" to the shell. Its goal was to cause the shell to abort any time an error occurred, but it comes with a lot of potential pitfalls for example,
The commands that are part of an if test are immune. In the example, if you expect it to break on the test check on the non-existing directory, it wouldn't, it goes through to the else condition
set -e
f() { test -d nosuchdir && echo no dir; }
f
echo survived
Commands in a pipeline other than the last one, are immune. In the example below, because the most recently executed (rightmost) command's exit code is considered ( cat) and it was successful. This could be avoided by setting by the set -o pipefail option but its still a caveat.
set -e
somecommand that fails | cat -
echo survived
Recommended for use - trap on exit
The verdict is if you want to be able to handle an error instead of blindly exiting, instead of using set -e, use a trap on the ERR pseudo signal.
The ERR trap is not to run code when the shell itself exits with a non-zero error code, but when any command run by that shell that is not part of a condition (like in if cmd, or cmd ||) exits with a non-zero exit status.
The general practice is we define an trap handler to provide additional debug information on which line and what cause the exit. Remember the exit code of the last command that caused the ERR signal would still be available at this point.
cleanup() {
exitcode=$?
printf 'error condition hit\n' 1>&2
printf 'exit code returned: %s\n' "$exitcode"
printf 'the command executing at the time of the error was: %s\n' "$BASH_COMMAND"
printf 'command present on line: %d' "${BASH_LINENO[0]}"
# Some more clean up code can be added here before exiting
exit $exitcode
}
and we just use this handler as below on top of the script that is failing
trap cleanup ERR
Putting this together on a simple script that contained false on line 15, the information you would be getting as
error condition hit
exit code returned: 1
the command executing at the time of the error was: false
command present on line: 15
The trap also provides options irrespective of the error to just run the cleanup on shell completion (e.g. your shell script exits), on signal EXIT. You could also trap on multiple signals at the same time. The list of supported signals to trap on can be found on the trap.1p - Linux manual page
Another thing to notice would be to understand that none of the provided methods work if you are dealing with sub-shells are involved in which case, you might need to add your own error handling.
On a sub-shell with set -e wouldn't work. The false is restricted to the sub-shell and never gets propagated to the parent shell. To do the error handling here, add your own logic to do (false) || false
set -e
(false)
echo survived
The same happens with trap also. The logic below wouldn't work for the reasons mentioned above.
trap 'echo error' ERR
(false)
Here's a simple trap that prints the last argument of whatever failed to STDERR, reports the line it failed on, and exits the script with the line number as the exit code. Note these are not always great ideas, but this demonstrates some creative application you could build on.
trap 'echo >&2 "$_ at $LINENO"; exit $LINENO;' ERR
I put that in a script with a loop to test it. I just check for a hit on some random numbers; you might use actual tests. If I need to bail, I call false (which triggers the trap) with the message I want to throw.
For elaborated functionality, have the trap call a processing function. You can always use a case statement on your arg ($_) if you need to do more cleanup, etc. Assign to a var for a little syntactic sugar -
trap 'echo >&2 "$_ at $LINENO"; exit $LINENO;' ERR
throw=false
raise=false
while :
do x=$(( $RANDOM % 10 ))
case "$x" in
0) $throw "DIVISION BY ZERO" ;;
3) $raise "MAGIC NUMBER" ;;
*) echo got $x ;;
esac
done
Sample output:
# bash tst
got 2
got 8
DIVISION BY ZERO at 6
# echo $?
6
Obviously, you could
runTest1 "Test1 fails" # message not used if it succeeds
Lots of room for design improvement.
The draw backs include the fact that false isn't pretty (thus the sugar), and other things tripping the trap might look a little stupid. Still, I like this method.
You have 2 options: Redirect the output of the script to a file, Introduce a log file in the script and
Redirecting output to a file:
Here you assume that the script outputs all necessary info, including warning and error messages. You can then redirect the output to a file of your choice.
./runTests &> output.log
The above command redirects both the standard output and the error output to your log file.
Using this approach you don't have to introduce a log file in the script, and so the logic is a tiny bit easier.
Introduce a log file to the script:
In your script add a log file either by hard coding it:
logFile='./path/to/log/file.log'
or passing it by a parameter:
logFile="${1}" # This assumes the first parameter to the script is the log file
It's a good idea to add the timestamp at the time of execution to the log file at the top of the script:
date '+%Y%-m%d-%H%M%S' >> "${logFile}"
You can then redirect your error messages to the log file
if [ condition ]; then
echo "Test cases failed!!" >> "${logFile}";
fi
This will append the error to the log file and continue execution. If you want to stop execution when critical errors occur, you can exit the script:
if [ condition ]; then
echo "Test cases failed!!" >> "${logFile}";
# Clean up if needed
exit 1;
fi
Note that exit 1 indicates that the program stop execution due to an unspecified error. You can customize this if you like.
Using this approach you can customize your logs and have a different log file for each component of your script.
If you have a relatively small script or want to execute somebody else's script without modifying it to the first approach is more suitable.
If you always want the log file to be at the same location, this is the better option of the 2. Also if you have created a big script with multiple components then you may want to log each part differently and the second approach is your only option.
I often find it useful to write a function to handle error messages so the code is cleaner overall.
# Usage: die [exit_code] [error message]
die() {
local code=$? now=$(date +%T.%N)
if [ "$1" -ge 0 ] 2>/dev/null; then # assume $1 is an error code if numeric
code="$1"
shift
fi
echo "$0: ERROR at ${now%???}${1:+: $*}" >&2
exit $code
}
This takes the error code from the previous command and uses it as the default error code when exiting the whole script. It also notes the time, with microseconds where supported (GNU date's %N is nanoseconds, which we truncate to microseconds later).
If the first option is zero or a positive integer, it becomes the exit code and we remove it from the list of options. We then report the message to standard error, with the name of the script, the word "ERROR", and the time (we use parameter expansion to truncate nanoseconds to microseconds, or for non-GNU times, to truncate e.g. 12:34:56.%N to 12:34:56). A colon and space are added after the word ERROR, but only when there is a provided error message. Finally, we exit the script using the previously determined exit code, triggering any traps as normal.
Some examples (assume the code lives in script.sh):
if [ condition ]; then die 123 "condition not met"; fi
# exit code 123, message "script.sh: ERROR at 14:58:01.234564: condition not met"
$command |grep -q condition || die 1 "'$command' lacked 'condition'"
# exit code 1, "script.sh: ERROR at 14:58:55.825626: 'foo' lacked 'condition'"
$command || die
# exit code comes from command's, message "script.sh: ERROR at 14:59:15.575089"
I dont know if it is weird that read is not taking the input from the terminal.
The configure script, which is used in source code making process, should ask the user to give the input to select the type of Database either MYSQL or ORACLE(below is the code).
MYSQLLIBPATH="/usr/lib/mysql"
echo "Enter DataBase-Type 1-ORACLE, 2-MySQL (default MySQL):"
read in
echo $? >> /tmp/error.log
if test -z "$in" -o "$in" = "2"
then
DATABASE=-DDB_MYSQL
if true; then
MYSQL_TRUE=
MYSQL_FALSE='#'
else
MYSQL_TRUE='#'
MYSQL_FALSE=
fi
echo "Enter Mysql Library Path: (eg: $MYSQLLIBPATH (default))"
read in
echo $? >> /tmp/error.log
if test -n "$in"
then
MYSQLLIBPATH=`echo $in`
fi
echo "Mysql Lib path is $MYSQLLIBPATH"
else
if false; then
MYSQL_TRUE=
MYSQL_FALSE='#'
else
MYSQL_TRUE='#'
MYSQL_FALSE=
fi
DATABASE=-DDB_ORACLE
LD_PATH=
fi
But, the read command is not asking for the user input. Its failing to take the input from the stdin.
When I checked the status of the command in the error.log it was showing
1
1
Could anyone tell why read is failing to take the input from the stdin.
Are there any builtin variable which can block read taking the input?
Most likely read executes with standard input redirected from a file that has reached EOF. If the above is not the whole of your configure code, check that there are no input redirections. Could the code above be a part of a function which was invoked with some input from a pipe or a file? Otherwise check how configure is executed - are there any redirections?
Otherwise, the universal advice applies: try simplifying and stripping down your code until it is obvious what's happening.
BTW, it is not a good idea to make configure interactive, if you want to have your program packaged for a distribution - it's not easy to control execution of interactive programs. Consider adding support for supplying parameters through command line options.
We have a wrapper script for Teradata TPT utility. The wrapper script is pretty straightforward but the problem is that the exit status of the wrapper is not the same as that of the utility. In many cases, the script returns 0 even if the utility fails. I have saved the exit status in a separate variable because some steps need to be done before exiting but exiting with this variable's value doesn't seem to work. Or is the utility returning status 0 even in case of some failures even if the logs clearly specify some other status?
The worse part is, this behavior is quite random, sometimes the script does fail with the exit status of the utility. I want to be sure if there is some problem with utility's exit status.
The script runs through KSH. The final part of the wrapper script is:
tbuild -f $sql.tmp -j ${id}_$JOB >$out 2>&1
ret_code=$?
cd ${TWB_ROOT}/logs
logpath=`ls -t ${TWB_ROOT}/logs/${id}_${JOB}*.out |head -1`
logpath1=${logpath##*/}
logname=${logpath1%-*}
tlogview -l ${logpath} > /edw/$GROUP/tnl/jobs/$JOB/logs/tpt_logs/${logname}.log
###Mainting 3 tpt binary log files
if [ $ret_code -eq 0 ]
then
binout=$TPTLOGDIR/${logname}.dat
binout1=$TPTLOGDIR/${logname}.dat1
binout2=$TPTLOGDIR/${logname}.dat2
[ -f $binout1 ] && mv $binout1 $binout2
[ -f $binout ] && mv $binout $binout1
mv "$logpath" "/edw/${GROUP}/tnl/jobs/$JOB/logs/tpt_logs/${logname}.dat"
fi
rm -f $sql.tmp
echo ".exit"
exit $ret_code
Thanks in advance for the help and suggestions.
The script looks ok, and should indeed return the same exit code as the tbuild utility.
It comes down to knowledge of the specific product.
I've never worked with any of these products, but Teradata has an ample User Guide for the Parallel Transporter, with an explicit Post-Job Considerations section, warning:
Even if the job completed successfully, action may still be required based on error and warning information in the job logs and error tables.
So technically, a job might complete, but results may vary from time to time.
I guess you have to define your own policies and scan the logfiles for patterns of warnings and error messages, and then generate your own exit codes for semantic failures. Tools like logstash or splunk might come in handy.
BTW, you might consider using logrotate for rotating the $TPTLOGDIR/${logname}.dat files.
Turns out that the issue was in the utility itself, as suspected. Shell script worked fine.