2.1.5 Context Line Control

Regardless of how these options are set, grep will never print any given line more than once. If the ‘-o’ (‘--only-matching’) option is specified, these options have no effect and a warning is given upon their use.

‘-A num’

‘--after-context=num’

Print num lines of trailing context after matching lines.

‘-B num’

‘--before-context=num’

Print num lines of leading context before matching lines.

‘-C num’

‘-num’

‘--context=num’

Print num lines of leading and trailing output context.

‘--group-separator=string’

When ‘-A’, ‘-B’ or ‘-C’ are in use, print string instead of ‘--’ between groups of lines.

‘--no-group-separator’

When ‘-A’, ‘-B’ or ‘-C’ are in use, do not print a separator between groups of lines.

Here are some points about how grep chooses the separator to print between prefix fields and line content:

• Matching lines normally use ‘:’ as a separator between prefix fields and actual line content.
• Context (i.e., non-matching) lines use ‘-’ instead.
• When context is not specified, matching lines are simply output one right after another.
• When context is specified, lines that are adjacent in the input form a group and are output one right after another, while by default a separator appears between non-adjacent groups.
• The default separator is a ‘--’ line; its presence and appearance can be changed with the options above.
• Each group may contain several matching lines when they are close enough to each other that two adjacent groups connect and can merge into a single contiguous one.

This document was generated on June 7, 2014 using texi2html 5.0.