Linux in a Nutshell, Fifth Edition

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Chapter 3: Linux Commands

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

Day of month 1-31

Month 1-12

Jan, Feb, Mar, ...

Day of week 0-6, with 0 = Sunday

Sun, Mon, Tue, ...

Use a comma between multiple values, a hyphen to indicate a

range, and an asterisk to indicate all possible values. For example,

assuming these crontab entries:

59 3 * * 5 find / -print | backup_program

0 0 1,15 * * echo "Timesheets due" | mail user

the first command backs up the system files every Friday at 3:59 a.m.,

and the second command mails a reminder on the 1st and 15th of

each month.

The superuser can always issue the crontab command. Other users

must be listed in the file /etc/cron.allow if it exists; otherwise, they

must not be listed in /etc/cron.deny. If neither file exists, only the

superuser can issue the command.

Options

The -e, -l, and -r options are not valid if any files are specified.

-e Edit the user’s current crontab file (or create one).

-l Display the user’s crontab file on standard output.

-r Delete the user’s crontab file.

-u user

Indicate which user’s crontab file will be acted upon.

csplit

csplit [options] file arguments

Separate file into context-based sections and place sections in files

named xx00 through xxn (n < 100), breaking file at each pattern

specified in arguments. See also split.

Options

- Read from standard input.

-b suffix, --suffix-format ...