Advanced Bash−Scripting Guide

Analyze Example A−11, and reorganize it in a simplified and more logical style. See how many of its
variables can be eliminated and try to optimize the script to speed up its execution time.
Alter the script so that it accepts any ordinary ASCII text file as input for its initial "generation". The script
will read the first $ROW*$COL characters, and set the occurrences of vowels as "living" cells. Hint: be sure to
translate the spaces in the input file to underscore characters.
I.2. Writing Scripts
Advanced Bash−Scripting Guide
Write a script to carry out each of the following tasks.
Easy
Home Directory Listing
Perform a recursive directory listing on the user's home directory and save the information to a file.
Compress the file, have the script prompt the user to insert a floppy, then press ENTER. Finally, save
the file to the floppy.
Converting for loops to while and until loops
Convert the for loops in Example 10−1 to while loops. Hint: store the data in an array and step
through the array elements.
Having already done the "heavy lifting", now convert the loops in the example to until loops.
Changing the line spacing of a text file
Write a script that reads each line of a target file, then writes the line back to stdout, but with an
extra blank line following. This has the effect of double−spacing the file.
Include all necessary code to check whether the script gets the necessary command line argument (a
filename), and whether the specified file exists.
When the script runs correctly, modify it to triple−space the target file.
Finally, write a script to remove all blank lines from the target file, single−spacing it.
Backwards Listing
Write a script that echoes itself to stdout, but backwards.
Automatically Decompressing Files
Given a list of filenames as input, this script queries each target file (parsing the output of the file
command) for the type of compression used on it. Then the script automatically invokes the
appropriate decompression command (gunzip, bunzip2, unzip, uncompress, or whatever). If a target
file is not compressed, the script emits a warning message, but takes no other action on that particular
file.
Unique System ID
Generate a "unique" 6−digit hexadecimal identifier for your computer. Do not use the flawed hostid
command. Hint: md5sum /etc/passwd, then select the first 6 digits of output.
Backup
Archive as a "tarball" (*.tar.gz file) all the files in your home directory tree
(/home/your−name) that have been modified in the last 24 hours. Hint: use find.
Primes
Print (to stdout) all prime numbers between 60000 and 63000. The output should be nicely formatted
in columns (hint: use printf).
Appendix I. Exercises 434