3.6 Less Frequently-Used Commands

Though perhaps less frequently used than those in the previous section, some very small yet useful sed scripts can be built with these commands.

y/source-chars/dest-chars/

(The / characters may be uniformly replaced by any other single character within any given y command.)

Transliterate any characters in the pattern space which match any of the source-chars with the corresponding character in dest-chars.

Instances of the / (or whatever other character is used in its stead), \, or newlines can appear in the source-chars or dest-chars lists, provide that each instance is escaped by a \. The source-chars and dest-chars lists must contain the same number of characters (after de-escaping).

a\

text

As a GNU extension, this command accepts two addresses.

Queue the lines of text which follow this command (each but the last ending with a \, which are removed from the output) to be output at the end of the current cycle, or when the next input line is read.

Escape sequences in text are processed, so you should use \\ in text to print a single backslash.

As a GNU extension, if between the a and the newline there is other than a whitespace-\ sequence, then the text of this line, starting at the first non-whitespace character after the a, is taken as the first line of the text block. (This enables a simplification in scripting a one-line add.) This extension also works with the i and c commands.

i\

text

As a GNU extension, this command accepts two addresses.

Immediately output the lines of text which follow this command (each but the last ending with a \, which are removed from the output).

c\

text

Delete the lines matching the address or address-range, and output the lines of text which follow this command (each but the last ending with a \, which are removed from the output) in place of the last line (or in place of each line, if no addresses were specified). A new cycle is started after this command is done, since the pattern space will have been deleted.

=

As a GNU extension, this command accepts two addresses.

Print out the current input line number (with a trailing newline).

l n

Print the pattern space in an unambiguous form: non-printable characters (and the \ character) are printed in C-style escaped form; long lines are split, with a trailing \ character to indicate the split; the end of each line is marked with a $.

n specifies the desired line-wrap length; a length of 0 (zero) means to never wrap long lines. If omitted, the default as specified on the command line is used. The n parameter is a GNU sed extension.

r filename

As a GNU extension, this command accepts two addresses.

Queue the contents of filename to be read and inserted into the output stream at the end of the current cycle, or when the next input line is read. Note that if filename cannot be read, it is treated as if it were an empty file, without any error indication.

As a GNU sed extension, the special value ‘/dev/stdin’ is supported for the file name, which reads the contents of the standard input.

w filename

Write the pattern space to filename. As a GNU sed extension, two special values of file-name are supported: ‘/dev/stderr’, which writes the result to the standard error, and ‘/dev/stdout’, which writes to the standard output.(5)

The file will be created (or truncated) before the first input line is read; all w commands (including instances of the w flag on successful s commands) which refer to the same filename are output without closing and reopening the file.

D

If pattern space contains no newline, start a normal new cycle as if the d command was issued. Otherwise, delete text in the pattern space up to the first newline, and restart cycle with the resultant pattern space, without reading a new line of input.

N

Add a newline to the pattern space, then append the next line of input to the pattern space. If there is no more input then sed exits without processing any more commands.

P

Print out the portion of the pattern space up to the first newline.

h

Replace the contents of the hold space with the contents of the pattern space.

H

Append a newline to the contents of the hold space, and then append the contents of the pattern space to that of the hold space.

g

Replace the contents of the pattern space with the contents of the hold space.

G

Append a newline to the contents of the pattern space, and then append the contents of the hold space to that of the pattern space.

x

Exchange the contents of the hold and pattern spaces.

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