running command from script it doesnt produce info

What are commandsĪ command is any word to be treated as a single point of entry of a program within the shell environment. We call commands of this category user-defined functions or functions for short. In order to execute function defined outside of a script, they must be declared with the -x attribute otherwise, they may be included using the. If it doesn’t, it proceeds down the order of precedence for commands. If it is the function is executed as a command. User-defined function (see functions)īefore executing external commands and builtins, bash checks if a function is defined. We call commands of this category, external commands, or commands for short. That is, if the curl command is in your path, it may be executed from within a bash script the same way as in interactive mode. This is observed in the case of the PATH variable including locations for executables that are referenced as external commands in bash. Executables in your environment (see external commands)īy default, bash will inherit certain variables by default. We call commands of this category, bash builtin commands, or builtins for short. Here we will lay down the foundation to execute commands from within a shell script answering the following questions about commands: Where do they come from? What are they? How do we use them in a script? Where do commands come from?Ĭommands in bash come from any of the following categories: Bash itself (see builtins)īash comes with its own set of commands to allow access to its built-in features such as declaring arrays, reading lines from a file, and other features builtin to bash. After all, commands executed within a bash script are not interactive.

So, both standard output and error will be redirected to /home/john/logs/backup.In bash, executing commands from a shell script can be a little intimidating at first and may require a leap of faith.

2>&1 indicates that the standard error (2>) is redirected to the same file descriptor that is pointed by standard output (&1).

> /home/john/logs/backup.log indicates that the standard output of the backup.sh script will be redirected to the backup.log file.$ crontab -eĥ9 23 * * * /home/john/bin/backup.sh > /home/john/logs/backup.log 2>&1 To do this, modify the crontab entry and add the output and error redirection as shown below. In general, if the backup.sh cron script throws any output (including errors), you might want to log those to a log file. If there are any echo statements inside the backup.sh, you might want to log those into a file. CMD – Anything following this is the real command that got executed at that time.Username – The username under which this cron job got executed.Hostname – The hostname of the server (For example, dev-db).Timestamp – The date and time when the cron job was executed.Oct 8 23:59:00 dev-db crond: (john) CMD (/bin/sh /home/john/bin/backup.sh &)Ĭron log contains the following information: Oct 8 23:00:00 dev-db crond: (oracle) CMD (/bin/sh /home/oracle/bin/cleanup.sh &) Oct 8 22:00:00 dev-db crond: (root) CMD (/bin/sh /home/root/bin/system_check &) As you see from the following output, john’s cron job got executed succesfully.

To verify whether the this job got executed successfully or not, check the /var/log/cron file, which contains information about all the cron jobs that gets executed in your system. How do I save the output of my script to a log file when it is executed as a cron job?Īnswer: Let us say that you’ve added the backup.sh to your crontab as shown below to execute it at midnight every day. How do I verify whether the backup cron script job ran successfully? Also, I have several echo statements inside my backup.sh shell script. Question: I created a backup.sh shell script and added it to my crontab to execute it daily.

Running command from script it doesnt produce info