MirBSD manpage: sed(1)

SED(1)                       BSD Reference Manual                       SED(1)


     sed - stream editor


     sed [-aEnru] [-i[extension]] command [file ...]
     sed [-aEnru] [-e command] [-f command_file] [-i[extension]] [file ...]


     The sed utility reads the specified files, or the standard input if no
     files are specified, modifying the input as specified by a list of com-
     mands. The input is then written to the standard output.

     A single command may be specified as the first argument to sed. Multiple
     commands may be specified separated by newlines or semicolons, or by us-
     ing the -e or -f options. All commands are applied to the input in the
     order they are specified regardless of their origin.

     The options are as follows:

     -a      The files listed as parameters for the w function or flag are
             created (or truncated) before any processing begins, by default.
             The -a option causes sed to delay opening each file until a com-
             mand containing the related w function or flag is applied to a
             line of input.

     -E      Interpret regular expressions using POSIX extended regular ex-
             pression syntax. The default behaviour is to use POSIX basic reg-
             ular expression syntax.

     -e command
             Append the editing commands specified by the command argument to
             the list of commands.

     -f command_file
             Append the editing commands found in the file command_file to the
             list of commands. The editing commands should each be listed on a
             separate line.

             Edit files in place, saving backups with the specified extension.
             If a zero length extension is given, no backup will be saved. It
             is not recommended to give a zero length extension when in place
             editing files, as it risks corruption or partial content in si-
             tuations where disk space is exhausted, etc.

     -r      An alias for -E, for compatibility with GNU sed.

     -n      By default, each line of input is echoed to the standard output
             after all of the commands have been applied to it. The -n option
             suppresses this behavior.

     -u      Force output to be line buffered, printing each line as it be-
             comes available. By default, output is line buffered when stan-
             dard output is a terminal and block buffered otherwise. See
             setvbuf(3) for a more detailed explanation.

     The form of a sed command is as follows:


     Whitespace may be inserted before the first address and the function por-
     tions of the command.

     Normally, sed cyclically copies a line of input, not including its ter-
     minating newline character, into a pattern space, (unless there is some-
     thing left after a D function), applies all of the commands with ad-
     dresses that select that pattern space, copies the pattern space to the
     standard output, appending a newline, and deletes the pattern space.

     Some of the functions use a hold space to save all or part of the pattern
     space for subsequent retrieval.


     An address is not required, but if specified must be a number (that
     counts input lines cumulatively across input files), a dollar character
     ('$') that addresses the last line of input, or a context address (which
     consists of a regular expression preceded and followed by a delimiter).

     A command line with no addresses selects every pattern space.

     A command line with one address selects all of the pattern spaces that
     match the address.

     A command line with two addresses selects the inclusive range from the
     first pattern space that matches the first address through the next pat-
     tern space that matches the second. (If the second address is a number
     less than or equal to the line number first selected, only that line is
     selected.) Starting at the first line following the selected range, sed
     starts looking again for the first address.

     Editing commands can be applied to non-selected pattern spaces by use of
     the exclamation character ('!') function.


     By default, sed regular expressions are basic regular expressions (BREs).
     Extended regular expressions are supported using the -E and -r options.
     See re_format(7) for more information on regular expressions. In addi-
     tion, sed has the following two additions to BREs:

     1.   In a context address, any character other than a backslash ('\') or
          newline character may be used to delimit the regular expression. The
          opening delimiter should be preceded by a backslash unless it is a
          slash. Putting a backslash character before the delimiting character
          causes the character to be treated literally. For example, in the
          context address \xabc\xdefx, the RE delimiter is an 'x' and the
          second 'x' stands for itself, so that the regular expression is

     2.   The escape sequence \n matches a newline character embedded in the
          pattern space. You can't, however, use a literal newline character
          in an address or in the substitute command.

          However, because sed cyclically copies a line of input, not includ-
          ing its terminating newline character, into a pattern space, you
          first must use the 'N' function to concatenate two lines, or do a
          similar trick, to get a newline into the pattern space.

     One special feature of sed regular expressions is that they can default
     to the last regular expression used. If a regular expression is empty,
     i.e., just the delimiter characters are specified, the last regular ex-
     pression encountered is used instead. The last regular expression is de-
     fined as the last regular expression used as part of an address or sub-
     stitute command, and at run-time, not compile-time. For example, the com-
     mand "/abc/s//XXX/" will substitute "XXX" for the pattern "abc".


     In the following list of commands, the maximum number of permissible ad-
     dresses for each command is indicated by [0addr], [1addr], or [2addr],
     representing zero, one, or two addresses.

     The argument text consists of one or more lines. To embed a newline in
     the text, precede it with a backslash. Other backslashes in text are
     deleted and the following character taken literally.

     The r and w functions, as well as the w flag to the s function, take an
     optional file parameter, which should be separated from the function or
     flag by whitespace. Files are created (or their contents truncated) be-
     fore any input processing begins.

     The b, r, s, t, w, y, and : functions all accept additional arguments.
     The synopses below indicate which arguments have to be separated from the
     function letters by whitespace characters.

     Functions can be combined to form a function list, a list of sed func-
     tions each followed by a newline, as follows:

           { function

     The braces can be preceded and followed by whitespace. The functions can
     be preceded by whitespace as well.

     Functions and function lists may be preceded by an exclamation mark, in
     which case they are applied only to lines that are not selected by the

             Execute function-list only when the pattern space is selected.

     [1addr]a\ text
             Write text to standard output immediately before each attempt to
             read a line of input, whether by executing the N function or by
             beginning a new cycle.

     [2addr]b [label]
             Branch to the : function with the specified label. If the label
             is not specified, branch to the end of the script.

     [2addr]c\ text
             Delete the pattern space. With 0 or 1 address or at the end of a
             2-address range, text is written to the standard output.

             Delete the pattern space and start the next cycle.

             Delete the initial segment of the pattern space through the first
             newline character and start the next cycle.

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

             Append a newline character followed by the contents of the hold
             space to the pattern space.

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

             Append a newline character followed by the contents of the pat-
             tern space to the hold space.

     [1addr]i\ text
             Write text to the standard output.

             (The letter ell.) Write the pattern space to the standard output
             in a visually unambiguous form. This form is as follows:

                   backslash          \\
                   alert              \a
                   backspace          \b
                   form-feed          \f
                   carriage-return    \r
                   tab                \t
                   vertical tab       \v

             Non-printable characters are written as three-digit octal numbers
             (with a preceding backslash) for each byte in the character (most
             significant byte first). Long lines are folded, with the point of
             folding indicated by displaying a backslash followed by a new-
             line. The end of each line is marked with a '$'.

             Write the pattern space to the standard output if the default
             output has not been suppressed, and replace the pattern space
             with the next line of input.

             Append the next line of input to the pattern space, using an em-
             bedded newline character to separate the appended material from
             the original contents. Note that the current line number changes.

             Write the pattern space to standard output.

             Write the pattern space, up to the first newline character, to
             the standard output.

             Branch to the end of the script and quit without starting a new

     [1addr]r file
             Copy the contents of file to the standard output immediately be-
             fore the next attempt to read a line of input. If file cannot be
             read for any reason, it is silently ignored and no error condi-
             tion is set.

             Substitute the replacement string for the first instance of the
             regular expression RE in the pattern space. Any character other
             than backslash or newline can be used instead of a slash to del-
             imit the regular expression and the replacement. Within the regu-
             lar expression and the replacement, the regular expression delim-
             iter itself can be used as a literal character if it is preceded
             by a backslash.

             An ampersand ('&') appearing in the replacement is replaced by
             the string matching the regular expression. The special meaning
             of '&' in this context can be suppressed by preceding it by a
             backslash. The string '\#', where '#' is a digit, is replaced by
             the text matched by the corresponding backreference expression
             (see re_format(7)).

             A line can be split by substituting a newline character into it.
             To specify a newline character in the replacement string, precede
             it with a backslash.

             The value of flags in the substitute function is zero or more of
             the following:

                   N       Make the substitution only for the N'th occurrence
                           of the regular expression in the pattern space,
                           where N is a positive integer starting with 1 ...

                   g       Make the substitution for all non-overlapping
                           matches of the regular expression, not just the
                           first one.

                   p       Write the pattern space to standard output if a re-
                           placement was made. If the replacement string is
                           identical to that which it replaces, it is still
                           considered to have been a replacement.

                   w file  Append the pattern space to file if a replacement
                           was made. If the replacement string is identical to
                           that which it replaces, it is still considered to
                           have been a replacement.

     [2addr]t [label]
             Branch to the : function bearing the label if any substitutions
             have been made since the most recent reading of an input line or
             execution of a t function. If no label is specified, branch to
             the end of the script.

     [2addr]w file
             Append the pattern space to the file.

             Swap the contents of the pattern and hold spaces.

             Replace all occurrences of characters in string1 in the pattern
             space with the corresponding characters from string2. Any charac-
             ter other than a backslash or newline can be used instead of a
             slash to delimit the strings. Within string1 and string2, a
             backslash followed by any character other than a newline is that
             literal character, and a backslash followed by an 'n' is replaced
             by a newline character.

             This function does nothing; it bears a label to which the b and t
             commands may branch.

             Write the line number to the standard output followed by a new-
             line character.

             Empty lines are ignored.

             The '#' and the remainder of the line are ignored (treated as a
             comment), with the single exception that if the first two charac-
             ters in the file are '#n', the default output is suppressed. This
             is the same as specifying the -n option on the command line.


     COLUMNS  If set to a positive integer, output from the l function is for-
              matted to the given width in columns. Otherwise, sed defaults to
              the terminal with, or 80 columns if the output is not a termi-


     The sed utility exits 0 on success, and >0 if an error occurs.


     The following simulates the cat(1) -s command, squeezing excess empty
     lines from standard input:

           $ sed -n '
           # Write non-empty lines.
           /./ {
           # Write a single empty line, then look for more empty lines.
           /^$/    p
           # Get the next line, discard the held <newline> (empty line),
           # and look for more empty lines.
           /^$/    {
               b Empty
           # Write the non-empty line before going back to search
           # for the first in a set of empty lines.


     awk(1), ed(1), grep(1), re_format(7)

     Lee E. McMahon, SED - A Non-interactive Text Editor, 15.sed(USD).


     The sed utility is compliant with the IEEE Std 1003.1-2008 ("POSIX.1")

     The flags [-aEiru] are extensions to that specification.

     The use of newlines to separate multiple commands on the command line is
     non-portable; the use of newlines to separate multiple commands within a
     command file (-f command_file) is portable.


     A sed command appeared in Version 7 AT&T UNIX.


     The use of semicolons to separate multiple commands is not permitted for
     the following commands: a, b, c, i, r, t, w, :, and #.

MirBSD #10-current             December 2, 2022                              5

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