Cron – Run Command with Existing Environmental Variables

cronenvironment-variablesshell

How can I run a cron command with existing environmental variables?

If I am at a shell prompt I can type echo $ORACLE_HOME and get a path. This is one of my environmental variables that gets set in my ~/.profile. However, it seems that ~/.profile does not get loaded fron cron scripts and so my scripts fail because the $ORACLE_HOME variable is not set.

In this question the author mentions creating a ~/.cronfile profile which sets up variables for cron, and then he does a workaround to load all his cron commands into scripts he keeps in his ~/Cron directory. A file like ~/.cronfile sounds like a good idea, but the rest of the answer seems a little cumbersome and I was hoping someone could tell me an easier way to get the same result.

I suppose at the start of my scripts I could add something like source ~/.profile but that seems like it could be redundant.

So how can I get make my cron scripts load the variables from my interactive-shell profile?

Best Answer

In the crontab, before you command, add . $HOME/.profile. For example:

0 5 * * * . $HOME/.profile; /path/to/command/to/run

Cron knows nothing about your shell; it is started by the system, so it has a minimal environment. If you want anything, you need to have that brought in yourself.

Related Solutions

Run Script in Non-Interactive Shell – Shell Scripting Tips

The main differences between running a command from cron and running on the command line are:

cron is probably using a different shell (generally /bin/sh);
cron is definitely running in a small environment (which ones depends on the cron implementation, so check the cron(8) or crontab(5) man page; generally there's just HOME, perhaps SHELL, perhaps LOGNAME, perhaps USER, and a small PATH);
cron treats the % character specially (it is turned into a newline);
cron jobs run without a terminal or graphical environment.

The following invocation will run the shell snippet pretty much as if it was invoked from cron. I assume the snippet doesn't contain the characters ' or %.

env - HOME="$HOME" USER="$USER" PATH=/usr/bin:/bin /bin/sh -c 'shell snippet' </dev/null >job.log 2>&1

See also executing a sh script from the cron, which might help solve your problem.

Bash – Fixing ‘stdin: is not a tty’ Mails for Running Scripts as Cron Jobs

Something in your .bashrc is assuming that the shell is running on a terminal. That's perfectly fine: .bashrc is supposed to run only in interactive shells, and interactive shells are supposed to run only on terminals.

The problem is that you're systematically including .bashrc from .profile. That's wrong: you should only include .bashrc in interactive shells.

Change your .profile to

# Bash doesn't load its interactive initialization file if it's invoked as
# a login shell, so do it manually.
case $- in
  *i*) if [ -n "$BASH" ]; then . ~/.bashrc;; fi
esac

Move mesg n into .bashrc: it's a terminal-related command, not a session-related command.

If you have environment variable definitions in your .bashrc, move them to .profile. The .profile file is for things that are executed when your session starts, typically mainly environment variable definitions, used by any application that you'll run during the session. The .bashrc file is the configuration file for bash when running interactively, it typically contains terminal setup, alias definitions, shell options and completion settings, and other things related to the interactive use of the shell.

For background, see:

Best Answer

Related Solutions

Run Script in Non-Interactive Shell – Shell Scripting Tips

Bash – Fixing ‘stdin: is not a tty’ Mails for Running Scripts as Cron Jobs

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