Cron Environment Variables – Interactive Shell Setup

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.

If it is an sh script - as in, it explicitly references #!/bin/sh - which might still be bash but would be like invoking it with --posix --no-rc --no-profile - then you can specify the ENV file with the ENV environment variable:

ENV=/path/to/rcfile sh

Specific variables need either to be declared on the command-line - as above for $ENV - or else with export. For example, for $PATH you do:

export "PATH=$PATH:/some/more/paths"; sh

The $BASH_ENV variable you reference is not a file you need to source - and it isn't interpreted anyway when bash is invoked as sh - but is rather a path to a file that is sourced when a non-interactive bash shell is invoked - such as with a script that specifies the:

#!/bin/bash

...or whatever bang line.

Another way you might like to invoke your script/shell is with the env utility. It can be used to explicitly remove values from the environment, or else, as is usually easiest, to wipe it clean from the start:

env - BASH_ENV=/path/to/rcfile /usr/bin/bash /some/script/file

That will tell env to invoke the /usr/bin/bash command - with all its arguments appended - with the $BASH_ENV environment variable specified, but otherwise with a clean environment entirely.