JavaScript is required to for searching.
Skip Navigation Links
Exit Print View
System Administration Guide: Advanced Administration
search filter icon
search icon

Document Information


1.  Managing Terminals and Modems (Overview)

2.  Setting Up Terminals and Modems (Tasks)

3.  Managing Serial Ports With the Service Access Facility (Tasks)

4.  Managing System Resources (Overview)

5.  Displaying and Changing System Information (Tasks)

6.  Managing Disk Use (Tasks)

7.  Managing UFS Quotas (Tasks)

8.  Scheduling System Tasks (Tasks)

Creating and Editing crontab Files (Task Map)

Ways to Automatically Execute System Tasks

For Scheduling Repetitive Jobs: crontab

For Scheduling a Single Job: at

Scheduling a Repetitive System Task (cron)

Inside a crontab File

How the cron Daemon Handles Scheduling

Syntax of crontab File Entries

Creating and Editing crontab Files

How to Create or Edit a crontab File

How to Verify That a crontab File Exists

Displaying crontab Files

How to Display a crontab File

Removing crontab Files

How to Remove a crontab File

Controlling Access to the crontab Command

How to Deny crontab Command Access

How to Limit crontab Command Access to Specified Users

How to Verify Limited crontab Command Access

Using the at Command (Task Map)

Scheduling a Single System Task (at)

Description of the at Command

Controlling Access to the at Command

How to Create an at Job

How to Display the at Queue

How to Verify an at Job

How to Display at Jobs

How to Remove at Jobs

How to Deny Access to the at Command

How to Verify That at Command Access Is Denied

9.  Managing System Accounting (Tasks)

10.  System Accounting (Reference)

11.  Managing System Performance (Overview)

12.  Managing System Processes (Tasks)

13.  Monitoring System Performance (Tasks)

14.  Troubleshooting Software Problems (Overview)

15.  Managing System Messages

16.  Managing Core Files (Tasks)

17.  Managing System Crash Information (Tasks)

18.  Troubleshooting Miscellaneous Software Problems (Tasks)

19.  Troubleshooting File Access Problems (Tasks)

20.  Resolving UFS File System Inconsistencies (Tasks)

21.  Troubleshooting Software Package Problems (Tasks)


Creating and Editing crontab Files

The simplest way to create a crontab file is to use the crontab -e command. This command invokes the text editor that has been set for your system environment. The default editor for your system environment is defined in the EDITOR environment variable. If this variable has not been set, the crontab command uses the default editor, ed. Preferably, you should choose an editor that you know well.

The following example shows how to determine if an editor has been defined, and how to set up vi as the default.

$ which $EDITOR
$ export EDITOR

When you create a crontab file, it is automatically placed in the /var/spool/cron/crontabs directory and is given your user name. You can create or edit a crontab file for another user, or root, if you have superuser privileges.

How to Create or Edit a crontab File

Before You Begin

If you are creating or editing a crontab file that belongs to root or another user you must become superuser or assume an equivalent role. Roles contain authorizations and privileged commands. For more information about roles, see Configuring RBAC (Task Map) in System Administration Guide: Security Services.

You do not need to become superuser to edit your own crontabfile.

  1. Create a new crontab file, or edit an existing file.
    $ crontab -e [username]

    where username specifies the name of the user's account for which you want to create or edit a crontab file. You can create your own crontab file without superuser privileges, but you must have superuser privileges to creating or edit a crontab file for root or another user.


    Caution - If you accidentally type the crontab command with no option, press the interrupt character for your editor. This character allows you to quit without saving changes. If you instead saved changes and exited the file, the existing crontab file would be overwritten with an empty file.

  2. Add command lines to the crontab file.

    Follow the syntax described in Syntax of crontab File Entries. The crontab file will be placed in the /var/spool/cron/crontabs directory.

  3. Verify your crontab file changes.
    # crontab -l [username]

Example 8-1 Creating a crontab File

The following example shows how to create a crontab file for another user.

# crontab -e jones

The following command entry added to a new crontab file automatically removes any log files from the user's home directory at 1:00 a.m. every Sunday morning. Because the command entry does not redirect output, redirect characters are added to the command line after *.log. Doing so ensures that the command executes properly.

# This command helps clean up user accounts.
1 0 * * 0 rm /home/jones/*.log > /dev/null 2>&1

How to Verify That a crontab File Exists