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6.4. When should I NOT use sed?

You should not use sed when you have "dedicated" tools which can do the job faster or with an easier syntax. Do not use sed when you only want to:

• print individual lines, based on patterns within the line itself. Instead, use "grep".
• print blocks of lines, with 1 or more lines of context above or below a specific regular expression. Instead, use the GNU version of grep as follows:

          grep -A{number} -B{number} "regex"
  

• remove individual lines, based on patterns within the line itself. Instead, use "grep -v".
• print line numbers. Instead, use "nl" or "cat -n".
• reformat lines or paragraphs. Instead, use "fold", "fmt" or "par".

The tr utility is also more suited than sed to some simple tasks. For example, to:

• delete individual characters. Instead of "s/[a-d]//g", use

          tr -d "[a-d]"
  

• squeeze sequential characters. Instead of "s/ee*/e/g", use

          tr -s "{character-set}"
  

• change individual characters. Instead of "y/abcdef/ABCDEF/", use

          tr "[a-f]" "[A-F]"
  

Note, however, that tr does not support giving input files on the command line, so the syntax is:

     tr {options-and-patterns} < input-file

or, to process multiple files:

     cat input-file1 input-file2 | tr {options-and-patterns}

If you have multiple files, using tr instead of sed is often more of an exercise than a useful thing. Although sed can perfectly emulate certain functions of cat, grep, nl, rev, sort, tac, tail, tr, uniq, and other utilities, producing identical output, the native utilities are usually optimized to do the job more quickly than sed.

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