Advanced Bash−Scripting Guide

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Advanced Bash−Scripting Guide
cpio
This specialized archiving copy command (copy input and output) is rarely seen any more, having
been supplanted by tar/gzip. It still has its uses, such as moving a directory tree.
Example 12−22. Using cpio to move a directory tree
#!/bin/bash
# Copying a directory tree using cpio.
ARGS=2
E_BADARGS=65
if [ $# −ne "$ARGS" ]
then
echo "Usage: `basename $0` source destination"
exit $E_BADARGS
fi
source=$1
destination=$2
find "$source" −depth | cpio −admvp "$destination"
# Read the man page to decipher these cpio options.
exit 0
rpm2cpio
This command extracts a cpio archive from an rpm one.
Example 12−23. Unpacking an rpm archive
#!/bin/bash
# de−rpm.sh: Unpack an 'rpm' archive
: ${1?"Usage: `basename $0` target−file"}
# Must specify 'rpm' archive name as an argument.
TEMPFILE=$$.cpio
# Tempfile with "unique" name.
# $$ is process ID of script.
rpm2cpio < $1 > $TEMPFILE
# Converts rpm archive into cpio archive.
cpio −−make−directories −F $TEMPFILE −i # Unpacks cpio archive.
rm −f $TEMPFILE
# Deletes cpio archive.
exit 0
# Exercise:
# Add check for whether 1) "target−file" exists and
#+ 2) it is really an rpm archive.
# Hint: parse output of 'file' command.
Compression
Chapter 12. External Filters, Programs and Commands 178