script does not write to file when executed from cron

Question

When I run a /bin/bash script, it works fine and it logs into some log files inside the script. But, when I run it from cron, it does not log to the file! it only logs to /var/mail/root , saying that

Date: Fri, 12 Aug 2016 08:39:01 +0300 (MSK)

/bin/sh: 1: root: not found

this is the script:

#!/bin/bash

LOG_FILE="test-crontab.log"
echo "started testing cron" >> ${LOG_FILE}

pgrep tunnel
if [[ ${?} != 0 ]]; then
  echo "Tunnel process is not running..." | tee -a ${LOG_FILE}
  echo "initializing tunnel..." | tee -a ${LOG_FILE}
  /usr/local/bin/stunnel | tee -a ${LOG_FILE} 2>&1
fi

echo `date` >> ${LOG_FILE}

and this is the cron:

45 8 * * *  /home/ubuntu/sam/scripts/sqlplus-scripts/accts-ct/test-crontab.sh > /dev/null

Solution

1. To get the log file where you expect it to be, replace:

   LOG_FILE="test-crontab.log"
   

   With:

   LOG_FILE="/home/ubuntu/sam/scripts/sqlplus-scripts/accts-ct/test-crontab.log"
   

2. The command [[ ${?} != 0 ]] is bash-only. From the error message that you quote, the script appears to be running under /bin/sh. One way to fix that is to replace:

   if [[ ${?} != 0 ]]; then
   

   With:

   if [ ${?} != 0 ]; then
   

   Another approach is to run crontab -e and add the following line to your crontab file:

   SHELL=/bin/bash
   

3. Also, for simplicity and style, consider replacing:

   echo `date` >> ${LOG_FILE}
   

   with:

   date >> "${LOG_FILE}"
   

   This eliminates a useless use of echo.

4. Lastly, consider putting double-quotes around all shell variables, particularly $LOG_FILE. Because the current value of LOG_FILE contains no spaces or shell-active characters, this is not needed now. But, putting double-quotes around them will will prevent unpleasant surprises in the future.

Comments

[John1024]

Two issues: (1) the script is running under sh but is using bash features, and (2) LOG_FILE should specify a complete path. (Neither of these issues, though, explains the error message.)

[Alex Lowe]

Did you do chmod u+x /home/ubuntu/sam/scripts/sqlplus-scripts/accts-ct/test-cront‌​ab.sh?

[Sam]

@Alex - yes it has x permission for all.

[Sam]

@john- it creates the file in the same folder script runs. So, that is not the issue. Script runs as expected when executed manually. about the sh, I think cron uses sh instead of bash. I don't know how to make it compatible

[John1024]

"it creates the file in the same folder script runs" According to the question, it wasn't writing to the file. Are you saying that the cron job does succeed in creating a file but fails to write to it?

[Sam]

no, I say if I run the script manually, it creates and writes to the file itself.

[John1024]

Please look in your home directory and see if a file named test-crontab.log exists there also.

[Sam]

yes! it has generated all the log files and script output zip files in the root directory! to solve the problem should I convert all absolute paths in the scripts to full path and then I think it will be fine. right?

[FKEinternet]

The user field is only present in crontab files saved in /etc/cron.d. In user-specific crontab files, the user field isn't present: The file's owner is the user.