Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
exit 0
run−parts
The run−parts command [33] executes all the scripts in a target directory, sequentially in
ASCII−sorted filename order. Of course, the scripts need to have execute permission.
yes
The crond daemon invokes run−parts to run the scripts in the /etc/cron.* directories.
In its default behavior the yes command feeds a continuous string of the character y followed by a
line feed to stdout. A control−c terminates the run. A different output string may be specified, as in
yes different string, which would continually output different string to stdout.
One might well ask the purpose of this. From the command line or in a script, the output of yes can be
redirected or piped into a program expecting user input. In effect, this becomes a sort of poor man's
version of expect.
yes | fsck /dev/hda1 runs fsck non−interactively (careful!).
yes | rm −r dirname has same effect as rm −rf dirname (careful!).
Caution advised when piping yes to a potentially dangerous system command, such as
fsck or fdisk. It may have unintended side−effects.
banner
Prints arguments as a large vertical banner to stdout, using an ASCII character (default '#'). This
may be redirected to a printer for hardcopy.
printenv
Show all the environmental variables set for a particular user.
bash$ printenv | grep HOME
HOME=/home/bozo
lp
The lp and lpr commands send file(s) to the print queue, to be printed as hard copy. [34] These
commands trace the origin of their names to the line printers of another era.
bash$ lp file1.txt or bash lp