Scripts run from cron must pick up a shared file of helper definitions. The definitions are in ~/.bashrc, but the scripts never see them because bash is started non-interactively. Which environment variable, when it names a file, causes a non-interactive bash to read that file at startup?
LPIC-1 Exam 102-500, objective 105. Shells and shell scripting hard
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The options
Correct BASH_ENV
Correct. When bash is started non-interactively it expands BASH_ENV and, if the result names a file, reads and executes it before running the script.
Not correct ENV
Wrong here, though it is the real POSIX counterpart. Bash consults ENV only when it is invoked as sh or is running in POSIX mode, not for an ordinary non-interactive bash.
Not correct BASH_SOURCE
Wrong. BASH_SOURCE is an array bash maintains itself, holding the source file names of the current call stack. Assigning to it does not cause anything to be read.
Not correct SHELLOPTS
Wrong. SHELLOPTS is a colon-separated list of the enabled set options. It changes shell behaviour flags, not which files are sourced.
Why
A non-interactive bash reads none of the usual startup files: not /etc/profile, not ~/.profile, not ~/.bashrc. Its one hook is BASH_ENV, whose value is expanded and then read as a file, and note that PATH is not used to find it, so give an absolute path. In practice the more robust answer for cron is to have the script source its helper file explicitly, since BASH_ENV must itself be set in cron's environment to have any effect.
Where this comes from
- Cited
- manual page bash(1)
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 105 and space the ones you get wrong.
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