Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
# Exercises:
# −−−−−−−−−
# 1) Add 'sed' commands to filter out other punctuation, such as commas.
# 2) Modify to also filter out multiple spaces and other whitespace.
# 3) Add a secondary sort key, so that instances of equal occurrence
#+ are sorted alphabetically.
exit 0
bash$ cat testfile
This line occurs only once.
This line occurs twice.
This line occurs twice.
This line occurs three times.
This line occurs three times.
This line occurs three times.
bash$ ./wf.sh testfile
6 this
6 occurs
6 line
3 times
3 three
2 twice
1 only
1 once
expand, unexpand
The expand filter converts tabs to spaces. It is often used in a pipe.
cut
The unexpand filter converts spaces to tabs. This reverses the effect of expand.
A tool for extracting fields from files. It is similar to the print $N command set in awk, but more
limited. It may be simpler to use cut in a script than awk. Particularly important are the −d (delimiter)
and −f (field specifier) options.
Using cut to obtain a listing of the mounted filesystems:
cat /etc/mtab | cut −d ' ' −f1,2
Using cut to list the OS and kernel version:
uname −a | cut −d" " −f1,3,11,12
Using cut to extract message headers from an e−mail folder:
bash$ grep '^Subject:' read−messages | cut −c10−80
Re: Linux suitable for mission−critical apps?
MAKE MILLIONS WORKING AT HOME!!!
Spam complaint
Re: Spam complaint
Using cut to parse a file:
Chapter 12. External Filters, Programs and Commands 162