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(sed.info)Addresses

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Enter node , (file) or (file)node

Selecting lines with SED
========================

   Addresses in a SED script can be in any of the following forms:
`NUMBER'
     Specifying a line number will match only that line in the input.
     (Note that SED counts lines continuously across all input files.)

`FIRST~STEP'
     This GNU extension matches every STEPth line starting with line
     FIRST.  In particular, lines will be selected when there exists a
     non-negative N such that the current line-number equals FIRST + (N
     * STEP).  Thus, to select the odd-numbered lines, one would use
     `1~2'; to pick every third line starting with the second, `2~3'
     would be used; to pick every fifth line starting with the tenth,
     use `10~5'; and `50~0' is just an obscure way of saying `50'.

`$'
     This address matches the last line of the last file of input.

`/REGEXP/'
     This will select any line which matches the regular expression
     REGEXP.  If REGEXP itself includes any `/' characters, each must
     be escaped by a backslash (`\').

`\%REGEXP%'
     (The `%' may be replaced by any other single character.)

     This also matches the regular expression REGEXP, but allows one to
     use a different delimiter than `/'.  This is particularly useful
     if the REGEXP itself contains a lot of `/'s, since it avoids the
     tedious escaping of every `/'.  If REGEXP itself includes any
     delimiter characters, each must be escaped by a backslash (`\').

`/REGEXP/I'
`\%REGEXP%I'
     The `I' modifier to regular-expression matching is a GNU extension
     which causes the REGEXP to be matched in a case-insensitive manner.

   If no addresses are given, then all lines are matched; if one
address is given, then only lines matching that address are matched.

   An address range can be specified by specifying two addresses
separated by a comma (`,').  An address range matches lines starting
from where the first address matches, and continues until the second
address matches (inclusively).  If the second address is a REGEXP, then
checking for the ending match will start with the line _following_ the
line which matched the first address.  If the second address is a
NUMBER less than (or equal to) the line matching the first address,
then only the one line is matched.

   Appending the `!' character to the end of an address specification
will negate the sense of the match.  That is, if the `!' character
follows an address range, then only lines which do _not_ match the
address range will be selected.  This also works for singleton
addresses, and, perhaps perversely, for the null address.