Discuss the structure of a crontab file and the guidelines for configuring its fields.
What will be an ideal response?
Each line in a crontab file defines a single cron job. There are six or seven fields in each line, separated by whitespace characters (spaces or tabs). The first five fields define when the cron job should be run. The sixth field in the line specifies the command to be run. If system jobs are defined, the sixth field contains the name of user to be used to run the job, and the seventh field specifies the command to be run.
The following are guidelines for configuring the first five fields:
• If you want a job to run every minute, hour, day, or month, type an asterisk (*) in the corresponding field.
• You can include several entries in a field in a list separated by commas.
• You can specify a range with start and end values separated by a hyphen.
• You can configure time steps with /n (where n represents the size of the step).
• You can specify months and weekdays using the first three letters of their names (for example, MON, TUE, JAN, FEB). The letters are not case sensitive. However, when you use letters, you cannot use ranges or lists.
• Numbers representing the weekdays start at 0 for Sunday and run through the entire week consecutively, with 7 representing Sunday again. For example, 3 is Wednesday and 6 is Saturday.
• If the first field starts with a - character and the job belongs to root, no log entry is written to the /var/log/messages file.
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What will be the effect of the following commands?
who | grep 'mary' who | grep '^mary' grep '[Uu]nix' ch?/* ls -l | sort -k4n sed '/^$/d' text > text.out sed 's/\([Uu]nix\)/\1(TM)/g' text > text.out date | cut -c12-16
An event log entry that is an error is marked with a red circle with a white exclamation point in the center.
Answer the following statement true (T) or false (F)
Answer the following statement(s) true (T) or false (F)
1. While Photoshop allows background editing, the Background layer cannot be moved.
2. Double-clicking the layer name opens the Layer Style dialog box.
3. When working with layers, it is important to make sure which layer you are editing by looking at the active layer on the Layers panel.
4. As shown in the accompanying figure, displaying thumbnails of each layer allows you to see easily what the layer looks like and helps you to be more efficient when editing a layer.
5. Were the accompanying figure to show more layers on the Layers panel, by default, those layers would be named alphabetically.