Quick ?s
Cheat Sheets
Man Pages
The Lynx
CRONTAB(1)							    CRONTAB(1)

       crontab - maintain crontab files for individual users (V3)

       crontab [ -u user ] file
       crontab [ -u user ] { -l | -r | -e }

       crontab	is  the  program used to install, deinstall or list the tables
       used to drive the cron(8) daemon in Vixie Cron.	 Each  user  can  have
       their	own    crontab,    and	  though    these    are    files   in
       /var/spool/cron/crontabs, they are not intended to be edited  directly.

       If  the /etc/cron.allow file exists, then you must be listed therein in
       order to be allowed to use this command.  If the  /etc/cron.allow  file
       does  not  exist  but the /etc/cron.deny file does exist, then you must
       not be listed in the /etc/cron.deny file in order to use this  command.
       If neither of these files exists, then depending on site-dependent con
       figuration parameters, only the super user will be allowed to use  this
       command,  or  all  users will be able to use this command. For standard
       Debian systems, all users may use this command.

       If the -u option is given, it specifies the  name  of  the  user  whose
       crontab	is  to be tweaked.  If this option is not given, crontab exam
       ines "your" crontab, i.e., the crontab of the person executing the com
       mand.   Note that su(8) can confuse crontab and that if you are running
       inside of su(8) you should always use the -u option for safetys	sake.

       The  first  form  of this command is used to install a new crontab from
       some named file or standard  input  if  the  pseudo-filename  -	is

       The  -l	option	causes the current crontab to be displayed on standard
       output. See the note under DEBIAN SPECIFIC below.

       The -r option causes the current crontab to be removed.

       The -e option is used to edit the  current  crontab  using  the	editor
       specified  by  the  VISUAL  or EDITOR environment variables.  After you
       exit from the editor, the modified crontab will be installed  automati
       cally.  If  neither  of	the environment variables is defined, then the
       default editor /usr/bin/editor is used.

       The "out-of-the-box" behaviour for crontab -l is to display  the  three
       line  "DO NOT EDIT THIS FILE" header that is placed at the beginning of
       the crontab when it is installed. The problem  is  that	it  makes  the

       crontab -l | crontab -

       non-idempotent  --  you	keep  adding copies of the header. This causes
       pain to scripts that use sed to edit a crontab. Therefore, the  default
       behaviour  of the -l option has been changed to not output such header.
       You may obtain the original behaviour by setting the environment  vari
       able  CRONTAB_NOHEADER  to N, which will cause the crontab -l command
       to emit the extraneous header.

       crontab(5), cron(8)


       The crontab command conforms to IEEE Std1003.2-1992 (POSIX).   This
       new  command  syntax  differs  from previous versions of Vixie Cron, as
       well as from the classic SVR3 syntax.

       A fairly informative usage message appears if you run  it  with	a  bad
       command line.

       Although  cron  requires  that each entry in a crontab end in a newline
       character, neither the crontab command nor the cron daemon will	detect
       this error. Instead, the crontab will appear to load normally. However,
       the command will never run. The best choice  is	to  ensure  that  your
       crontab has a blank line at the end.

       Paul Vixie 

4th Berkeley Distribution      29 December 1993 		    CRONTAB(1)

Yals.net is © 1999-2009 Crescendo Communications
Sharing tech info on the web for more than a decade!
This page was generated Thu Apr 30 17:05:18 2009