4.4 Unix-like text processing

There are few standard text processing tools which are used very often on the Unix-like system.

• No regular expression is used:

  • head outputs the first part of files.

  • tail outputs the last part of files.

  • sort sorts lines of text files.

  • uniq removes duplicate lines from a sorted file.

  • tr translates or deletes characters.

  • diff compares files line by line.

• Basic regular expression (BRE) is used:

  • grep matches text with the pattern.

  • ed is a primitive line editor.

  • sed is a stream editor.

  • vi is a screen editor.

  • emacs is a screen editor.

• Extended regular expression (ERE) is used:

  • egrep matches text with pattern.

  • awk does simple text processing. See Awk, Section 13.3.

  • perl does every conceivable text processing. See Perl, Section 13.4.

See Regular-expression substitution, Section 8.6.13, Script snippets for piping commands, Section 8.6.18, and Perl short script madness, Section 8.6.20 for some script examples.