README

Bash is not a general-purpose programming language. It is a language for programming the shell, which provides an interface to access the services of a Linux operating system. Despite its ancient syntax and crippling limitations, Bash remains relevant today for managing system programs and automating small tasks in a Linux environment. Bash is certainly worth learning.

To illustrate the utility of Bash, imagine that you are asked to write

A program that reads a text file and prints a table of unique words and corresponding frequencies, sorted from most to least frequent.

In 1986, Donald Knuth, the Father of the analysis of computer algorithms, was asked to write such a program. He produced a solution in Pascal that was 10 pages in length. This code was well-designed, thoroughly commented, and introduced a novel data structure. The same task can be achieved by the following 5-line Bash script:

tr -cs A-Za-z '\n' |    # put each word on its own line
tr A-Z a-z |            # convert all uppercase letters to lower case
sort |                  # sort the words alphabetically
uniq -c |               # create a frequency table for unique words
sort -k 1rn -k 2        # sort by descending frequency, then lexicographically

The reason why this Bash script is so terse is because it does not start from scratch; rather, it feeds the input through a series of existing programs to produce the desired output. Bash breaks down a complex task into smaller jobs that it delegates to specialized Linux programs.

Indeed, Bash excels in work flow management. While Bash is a poor choice for writing fault-tolerant, memory-intensive, performance-critical applications, it is a widely used language for managing programs in the Linux environment. With this guide, you will learn to write simple and comprehensible Bash scripts, allowing you to achieve the full potential of Linux.