I have a CRONTAB entry as below. Can someone tell me what the below statement is exactly doing?
1 0 * * * /vol01/sites/provisioning/MNMS/45627/45627.sh1 >> /vol01/sites/provisioning/MNMS/45627/output/cron.log 2>&1
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3See [What is the difference between > and >> (especially as it relates to use with the cat program)?](http://unix.stackexchange.com/questions/46974/what-is-the-difference-between-and-especially-as-it-relates-to-use-with-th), [What does “3>&1 1>&2 2>&3” do in a script?](http://unix.stackexchange.com/questions/42728/what-does-31-12-23-do-in-a-script) and of course, your shell's manual. (There are some further explanations in [Is this a typo in Bash manual's redirection section?](http://unix.stackexchange.com/questions/84279/is-this-a-typo-in-bash-manuals-redirection-section) too.) – manatwork Sep 04 '13 at 10:08
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@mana ....thanks a lot very useful articles.. – user3475 Sep 05 '13 at 04:02
2 Answers
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> redirects output to a file, overwriting the file.
>> redirects output to a file appending the redirected output at the end.
Standard output is represented in bash with number 1 and standard error is represented with number 2. They are separate, so the user can redirect them to different files.
2>&1 redirects the standard error to the standard output so they appear together and can be jointly redirected to a file. (Writing just 2>1 would redirect the standard error to a file called "1", not to standard output.)
In your case, you have a job whose output (both standard and error) is appended at the end of a log file (cron.log) for later use.
For additional info, check the bash manual (section "Redirection"), this question, and this question.
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You should google with keyword bash redirection for some detailed information. Here is a nice article for reference.
For your question, the crontab will run 45627.sh1 scripts at 00:01 everyday and append its error and output to the cron.log file.
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Thanks a lot. It really helps. Now I understood Google can't give everything. Experts advice always best :) – user3475 Sep 04 '13 at 12:54