sed(1p) - phpMan

SED(1P)                    POSIX Programmer's Manual                   SED(1P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       sed - stream editor
SYNOPSIS
       sed [-n] script[file...]
       sed [-n][-e script]...[-f script_file]...[file...]

DESCRIPTION
       The sed utility is a stream editor that shall read  one  or  more  text
       files,  make editing changes according to a script of editing commands,
       and write the results to standard output. The script shall be  obtained
       from  either  the script operand string or a combination of the option-
       arguments from the -e script and -f script_file options.
OPTIONS
       The sed utility  shall  conform  to  the  Base  Definitions  volume  of
       IEEE Std 1003.1-2001,  Section  12.2, Utility Syntax Guidelines, except
       that the order of presentation of the -e and -f options is significant.
       The following options shall be supported:
       -e  script
              Add the editing commands specified by the script option-argument
              to the end of the script of editing commands. The script option-
              argument shall have the same properties as the  script  operand,
              described in the OPERANDS section.
       -f  script_file
              Add  the  editing commands in the file script_file to the end of
              the script.
       -n     Suppress the default output (in which each  line,  after  it  is
              examined for editing, is written to standard output). Only lines
              explicitly selected for output are written.

       Multiple -e and -f options may be  specified.  All  commands  shall  be
       added to the script in the order specified, regardless of their origin.
OPERANDS
       The following operands shall be supported:
       file   A pathname of a file whose contents are read and edited. If mul-
              tiple file operands are specified, the named files shall be read
              in  the  order  specified and the concatenation shall be edited.
              If no file operands are specified, the standard input  shall  be
              used.
       script A  string  to  be  used  as  the script of editing commands. The
              application  shall  not  present  a  script  that  violates  the
              restrictions of a text file except that the final character need
              not be a <newline>.

STDIN
       The standard input shall be used only if no file  operands  are  speci-
       fied. See the INPUT FILES section.
INPUT FILES
       The  input  files shall be text files. The script_files named by the -f
       option shall consist of editing commands.
ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of sed:
       LANG   Provide a default value for the  internationalization  variables
              that  are  unset  or  null.  (See the Base Definitions volume of
              IEEE Std 1003.1-2001, Section  8.2,  Internationalization  Vari-
              ables  for the precedence of internationalization variables used
              to determine the values of locale categories.)
       LC_ALL If set to a non-empty string value, override the values  of  all
              the other internationalization variables.
       LC_COLLATE
              Determine  the  locale  for  the behavior of ranges, equivalence
              classes, and multi-character collating elements  within  regular
              expressions.
       LC_CTYPE
              Determine  the  locale  for  the  interpretation of sequences of
              bytes of text data as characters (for  example,  single-byte  as
              opposed  to multi-byte characters in arguments and input files),
              and the behavior of character  classes  within  regular  expres-
              sions.
       LC_MESSAGES
              Determine  the  locale  that should be used to affect the format
              and contents of diagnostic messages written to standard error.
       NLSPATH
              Determine the location of message catalogs for the processing of
              LC_MESSAGES .

ASYNCHRONOUS EVENTS
       Default.
STDOUT
       The  input  files shall be written to standard output, with the editing
       commands specified in the script applied. If the -n  option  is  speci-
       fied, only those input lines selected by the script shall be written to
       standard output.
STDERR
       The standard error shall be used only for diagnostic messages.
OUTPUT FILES
       The output files shall be text files whose formats are dependent on the
       editing commands given.
EXTENDED DESCRIPTION
       The script shall consist of editing commands of the following form:

              [address[,address]]function
       where function represents a single-character command verb from the list
       in Editing Commands in sed, followed by any applicable arguments.
       The command can be preceded by <blank>s and/or semicolons. The function
       can  be  preceded  by <blank>s. These optional characters shall have no
       effect.
       In default operation, sed cyclically shall append a line of input, less
       its terminating <newline>, into the pattern space. Normally the pattern
       space will be empty, unless a D command terminated the last cycle.  The
       sed  utility  shall then apply in sequence all commands whose addresses
       select that pattern space, and at the end of the script copy  the  pat-
       tern  space to standard output (except when -n is specified) and delete
       the pattern space. Whenever the pattern space is  written  to  standard
       output  or  a  named file, sed shall immediately follow it with a <new-
       line>.
       Some of the editing commands use a hold space to save all  or  part  of
       the pattern space for subsequent retrieval. The pattern and hold spaces
       shall each be able to hold at least 8192 bytes.
   Addresses in sed
       An address is either a decimal number that counts input  lines  cumula-
       tively  across  files,  a '$' character that addresses the last line of
       input, or a context address (which consists of a BRE, as  described  in
       Regular  Expressions in sed, preceded and followed by a delimiter, usu-
       ally a slash).
       An editing command with no addresses shall select every pattern space.
       An editing command with one address shall  select  each  pattern  space
       that matches the address.
       An  editing command with two addresses shall select the inclusive range
       from the first pattern space that matches the first address through the
       next pattern space that matches the second. (If the second address is a
       number less than or equal to the line number first selected,  only  one
       line  shall  be  selected.)  Starting  at  the first line following the
       selected range, sed shall look again for the first address. Thereafter,
       the  process  shall be repeated. Omitting either or both of the address
       components in the following form produces undefined results:

              [address[,address]]
   Regular Expressions in sed
       The sed utility shall support the BREs described in  the  Base  Defini-
       tions  volume  of  IEEE Std 1003.1-2001,  Section  9.3,  Basic  Regular
       Expressions, with the following additions:
        * In a context address, the construction  "\cBREc",  where  c  is  any
          character  other  than backslash or <newline>, shall be identical to
          "/BRE/" . If the character designated by c appears following a back-
          slash,  then  it  shall  be considered to be that literal character,
          which shall not terminate the  BRE.  For  example,  in  the  context
          address  "\xabc\xdefx",  the second x stands for itself, so that the
          BRE is "abcxdef" .
        * The escape sequence '\n' shall match a  <newline>  embedded  in  the
          pattern space. A literal <newline> shall not be used in the BRE of a
          context address or in the substitute function.
        * If an RE is empty (that is,  no  pattern  is  specified)  sed  shall
          behave as if the last RE used in the last command applied (either as
          an address or as part of a substitute command) was specified.
   Editing Commands in sed
       In the following list of editing commands, the maximum number  of  per-
       missible  addresses  for  each  function  is  indicated  by [ 0addr], [
       1addr], or [ 2addr], representing zero, one, or two addresses.
       The argument text shall consist of one or  more  lines.  Each  embedded
       <newline>  in  the  text  shall be preceded by a backslash. Other back-
       slashes in text shall be removed, and the following character shall  be
       treated literally.
       The  r  and  w  command verbs, and the w flag to the s command, take an
       optional rfile (or wfile) parameter, separated from  the  command  verb
       letter  or flag by one or more <blank>s; implementations may allow zero
       separation as an extension.
       The argument rfile or the argument wfile shall  terminate  the  editing
       command.  Each  wfile shall be created before processing begins. Imple-
       mentations shall support at least ten wfile arguments  in  the  script;
       the  actual  number  (greater than or equal to 10) that is supported by
       the implementation is unspecified. The use of the wfile parameter shall
       cause that file to be initially created, if it does not exist, or shall
       replace the contents of an existing file.
       The b, r, s, t, w, y, and : command verbs shall accept additional argu-
       ments.   The following synopses indicate which arguments shall be sepa-
       rated from the command verbs by a single <space>.
       The a and r commands schedule text for later output. The text specified
       for  the  a  command,  and the contents of the file specified for the r
       command, shall be written to  standard  output  just  before  the  next
       attempt to fetch a line of input when executing the N or n commands, or
       when reaching the end of the script. If written when reaching  the  end
       of  the  script, and the -n option was not specified, the text shall be
       written after copying the pattern space to standard  output.  The  con-
       tents  of  the file specified for the r command shall be as of the time
       the output is written, not the time the r command is applied. The  text
       shall be output in the order in which the a and r commands were applied
       to the input.
       Command verbs other than {, a, b, c, i, r, t, w, :, and # can  be  fol-
       lowed by a semicolon, optional <blank>s, and another command verb. How-
       ever, when the s command verb is used with the  w  flag,  following  it
       with another command in this manner produces undefined results.
       A function can be preceded by one or more '!' characters, in which case
       the function shall be applied if the addresses do not select  the  pat-
       tern  space.  Zero  or more <blank>s shall be accepted before the first
       '!' character. It is unspecified whether  <blank>s  can  follow  a  '!'
       character,  and conforming applications shall not follow a '!'  charac-
       ter with <blank>s.
       [2addr] {function
       function
       ...
       }      Execute a list of sed functions only when the pattern  space  is
              selected.  The  list  of  sed  functions  shall be surrounded by
              braces and separated by <newline>s, and conform to the following
              rules.  The  braces can be preceded or followed by <blank>s. The
              functions can be preceded by <blank>s, but shall not be followed
              by  <blank>s. The <right-brace> shall be preceded by a <newline>
              and can be preceded or followed by <blank>s.
       [1addr]a\
       text   Write text to standard output as described previously.
       [2addr]b [label]
              Branch to the : function bearing the  label.  If  label  is  not
              specified,  branch  to the end of the script. The implementation
              shall support labels recognized as unique up to at least 8 char-
              acters;  the  actual  length  (greater  than or equal to 8) that
              shall be supported by the implementation is unspecified.  It  is
              unspecified  whether exceeding a label length causes an error or
              a silent truncation.
       [2addr]c\
       text   Delete the pattern space. With a 0 or 1 address or at the end of
              a  2-address  range, place text on the output and start the next
              cycle.
       [2addr]d
              Delete the pattern space and start the next cycle.
       [2addr]D
              Delete the initial segment of  the  pattern  space  through  the
              first <newline> and start the next cycle.
       [2addr]g
              Replace the contents of the pattern space by the contents of the
              hold space.
       [2addr]G
              Append to the pattern space a <newline> followed by the contents
              of the hold space.
       [2addr]h
              Replace  the contents of the hold space with the contents of the
              pattern space.
       [2addr]H
              Append to the hold space a <newline> followed by the contents of
              the pattern space.
       [1addr]i\
       text   Write text to standard output.
       [2addr]l
              (The  letter ell.) Write the pattern space to standard output in
              a visually unambiguous form. The characters listed in  the  Base
              Definitions  volume  of  IEEE Std 1003.1-2001, Table 5-1, Escape
              Sequences and Associated Actions ( '\\', '\a', '\b', '\f', '\r',
              '\t',  '\v'  )  shall  be  written  as  the corresponding escape
              sequence; the '\n' in that table is not  applicable.  Non-print-
              able characters not in that table shall be written as one three-
              digit octal number (with a preceding backslash) for each byte in
              the  character  (most  significant byte first). If the size of a
              byte on the system is greater than 9 bits, the format  used  for
              non-printable characters is implementation-defined.
       Long  lines  shall  be  folded,  with the point of folding indicated by
       writing a backslash followed by a <newline>; the length at which  fold-
       ing  occurs  is  unspecified,  but should be appropriate for the output
       device. The end of each line shall be marked with a '$' .
       [2addr]n
              Write the pattern space to standard output if the default output
              has  not been suppressed, and replace the pattern space with the
              next line of input, less its terminating <newline>.
       If no next line of input is available, the n command verb shall  branch
       to the end of the script and quit without starting a new cycle.
       [2addr]N
              Append  the  next line of input, less its terminating <newline>,
              to the pattern space, using an embedded  <newline>  to  separate
              the  appended material from the original material. Note that the
              current line number changes.
       If no next line of input is available, the N command verb shall  branch
       to the end of the script and quit without starting a new cycle or copy-
       ing the pattern space to standard output.
       [2addr]p
              Write the pattern space to standard output.
       [2addr]P
              Write the pattern space, up to the first <newline>, to  standard
              output.
       [1addr]q
              Branch  to the end of the script and quit without starting a new
              cycle.
       [1addr]r  rfile
              Copy the contents of rfile to standard output as described  pre-
              viously.  If rfile does not exist or cannot be read, it shall be
              treated as if it were an empty file, causing no error condition.
       [2addr]s/BRE/replacement/flags
              Substitute the replacement string for instances of  the  BRE  in
              the  pattern  space. Any character other than backslash or <new-
              line> can be used instead of a slash to delimit the BRE and  the
              replacement.  Within the BRE and the replacement, the BRE delim-
              iter itself can be used as a literal character if it is preceded
              by a backslash.
       The  replacement  string  shall  be  scanned  from beginning to end. An
       ampersand ( '&' ) appearing in the replacement shall be replaced by the
       string matching the BRE. The special meaning of '&' in this context can
       be suppressed by preceding it by  a  backslash.  The  characters  "\n",
       where n is a digit, shall be replaced by the text matched by the corre-
       sponding backreference expression. The special meaning of "\n" where  n
       is  a  digit  in  this  context, can be suppressed by preceding it by a
       backslash. For each other backslash ( '\' ) encountered, the  following
       character shall lose its special meaning (if any). The meaning of a '\'
       immediately followed by any character other than '&', '\', a digit,  or
       the delimiter character used for this command, is unspecified.
       A  line  can be split by substituting a <newline> into it. The applica-
       tion shall escape the <newline> in the replacement by preceding it by a
       backslash.  A  substitution  shall be considered to have been performed
       even if the replacement string is  identical  to  the  string  that  it
       replaces.  Any  backslash used to alter the default meaning of a subse-
       quent character shall be discarded from  the  BRE  or  the  replacement
       before evaluating the BRE or using the replacement.
       The value of flags shall be zero or more of:
       n
              Substitute  for  the nth occurrence only of the BRE found within
              the pattern space.
       g
              Globally substitute for all non-overlapping instances of the BRE
              rather  than  just the first one. If both g and n are specified,
              the results are unspecified.
       p
              Write the pattern space to standard output if a replacement  was
              made.
       w  wfile
              Write.  Append  the  pattern space to wfile if a replacement was
              made. A conforming application shall precede the wfile  argument
              with  one  or  more <blank>s. If the w flag is not the last flag
              value given in a concatenation  of  multiple  flag  values,  the
              results are undefined.

       [2addr]t [label]
              Test. Branch to the : command verb bearing the label if any sub-
              stitutions have been made since the most recent  reading  of  an
              input  line  or  execution  of  a  t. If label is not specified,
              branch to the end of the script.
       [2addr]w  wfile
              Append (write) the pattern space to wfile.
       [2addr]x
              Exchange the contents of the pattern and hold spaces.
       [2addr]y/string1/string2/
              Replace all occurrences of characters in string1 with the corre-
              sponding  characters  in  string2. If a backslash followed by an
              'n' appear in string1 or string2, the two  characters  shall  be
              handled  as  a  single <newline>. If the number of characters in
              string1 and string2 are not equal, or if any of  the  characters
              in string1 appear more than once, the results are undefined. Any
              character other than backslash or <newline> can be used  instead
              of  slash  to  delimit  the  strings. If the delimiter is not n,
              within string1 and string2, the delimiter itself can be used  as
              a  literal  character  if  it  is preceded by a backslash.  If a
              backslash character is immediately followed by a backslash char-
              acter  in string1 or string2, the two backslash characters shall
              be counted as a single literal backslash character. The  meaning
              of  a  backslash  followed  by  any character that is not 'n', a
              backslash, or the delimiter character is undefined.
       [0addr]:label
              Do nothing. This command bears a label to which the b and t com-
              mands branch.
       [1addr]=
              Write the following to standard output:

              "%d\n", <current line number>
       [0addr]
              Ignore this empty command.
       [0addr]#
              Ignore  the  '#'  and the remainder of the line (treat them as a
              comment), with the single exception that if the first two  char-
              acters  in the script are "#n", the default output shall be sup-
              pressed; this shall be the equivalent of specifying  -n  on  the
              command line.

EXIT STATUS
       The following exit values shall be returned:
        0     Successful completion.
       >0     An error occurred.

CONSEQUENCES OF ERRORS
       Default.
       The following sections are informative.
APPLICATION USAGE
       Regular  expressions  match  entire strings, not just individual lines,
       but a <newline> is matched by '\n' in a sed  RE;  a  <newline>  is  not
       allowed   by   the   general   definition   of  regular  expression  in
       IEEE Std 1003.1-2001.  Also note that '\n' cannot be used  to  match  a
       <newline>  at  the end of an arbitrary input line; <newline>s appear in
       the pattern space as a result of the N editing command.
EXAMPLES
       This sed script simulates the BSD  cat  -s  command,  squeezing  excess
       blank lines from standard input.

              sed -n '
              # Write non-empty lines.
              /./ {
                  p
                  d
                  }
              # Write a single empty line, then look for more empty lines.
              /^$/    p
              # Get next line, discard the held <newline> (empty line),
              # and look for more empty lines.
              :Empty
              /^$/    {
                  N
                  s/.//
                  b Empty
                  }
              # Write the non-empty line before going back to search
              # for the first in a set of empty lines.
                  p
RATIONALE
       This volume of IEEE Std 1003.1-2001 requires implementations to support
       at least ten distinct wfiles,  matching  historical  practice  on  many
       implementations.  Implementations  are  encouraged to support more, but
       conforming applications should not exceed this limit.
       The exit status codes specified here are different from those in System
       V.  System  V returns 2 for garbled sed commands, but returns zero with
       its usage message or if the input file could not be opened.  The  stan-
       dard developers considered this to be a bug.
       The  manner  in which the l command writes non-printable characters was
       changed to avoid the historical backspace-overstrike method, and  other
       requirements  to  achieve unambiguous output were added. See the RATIO-
       NALE for ed for details of the format chosen, which is the same as that
       chosen for sed.
       This volume of IEEE Std 1003.1-2001 requires implementations to provide
       pattern and hold spaces of at least 8192 bytes, larger  than  the  4000
       bytes spaces used by some historical implementations, but less than the
       20480 bytes limit  used  in  an  early  proposal.  Implementations  are
       encouraged  to  allocate  dynamically larger pattern and hold spaces as
       needed.
       The requirements for acceptance of <blank>s  and  <space>s  in  command
       lines  has  been made more explicit than in early proposals to describe
       clearly the historical practice  and  to  remove  confusion  about  the
       phrase  "protect  initial blanks [sic] and tabs from the stripping that
       is done on every script line" that appears in much  of  the  historical
       documentation  of  the sed utility description of text. (Not all imple-
       mentations are  known  to  have  stripped  <blank>s  from  text  lines,
       although  they  all have allowed leading <blank>s preceding the address
       on a command line.)
       The treatment of '#' comments differs from the SVID which only allows a
       comment as the first line of the script, but matches BSD-derived imple-
       mentations. The comment character is treated as a command, and  it  has
       the  same  properties in terms of being accepted with leading <blank>s;
       the BSD implementation has historically supported this.
       Early proposals required that a script_file have at least one  non-com-
       ment  line.  Some historical implementations have behaved in unexpected
       ways if this were not the case. The standard developers considered that
       this  was incorrect behavior and that application developers should not
       have to avoid this feature. A correct implementation of this volume  of
       IEEE Std 1003.1-2001  shall  permit  script_files  that consist only of
       comment lines.
       Early proposals indicated that if -e and -f  options  were  intermixed,
       all  -e  options  were  processed  before any -f options. This has been
       changed to process them in the order presented because it matches  his-
       torical practice and is more intuitive.
       The  treatment  of the p flag to the s command differs between System V
       and BSD-based systems when the default output is suppressed. In the two
       examples:

              echo a | sed    's/a/A/p'
              echo a | sed -n 's/a/A/p'
       this  volume  of IEEE Std 1003.1-2001, BSD, System V documentation, and
       the SVID indicate that the first example should write two lines with A,
       whereas the second should write one.  Some System V systems write the A
       only once in both examples because the p flag  is  ignored  if  the  -n
       option is not specified.
       This  is  a case of a diametrical difference between systems that could
       not be reconciled through the compromise of declaring the  behavior  to
       be  unspecified.  The  SVID/BSD/System  V  documentation  behavior  was
       adopted for this volume of IEEE Std 1003.1-2001 because:
        * No known documentation for any historic system describes the  inter-
          action between the p flag and the -n option.
        * The  selected behavior is more correct as there is no technical jus-
          tification for any interaction between the p flag and the -n option.
          A  relationship  between -n and the p flag might imply that they are
          only used together, but this ignores valid  scripts  that  interrupt
          the  cyclical  nature of the processing through the use of the D, d,
          q, or branching commands. Such scripts rely on the p suffix to write
          the pattern space because they do not make use of the default output
          at the "bottom" of the script.
        * Because the -n option makes the p flag unnecessary, any  interaction
          would  only  be  useful if sed scripts were written to run both with
          and without the -n option. This is believed to be  unlikely.  It  is
          even  more unlikely that programmers have coded the p flag expecting
          it to be unnecessary.  Because the interaction was  not  documented,
          the  likelihood  of  a  programmer  discovering  the interaction and
          depending on it is further decreased.
        * Finally, scripts that break under the specified behavior produce too
          much  output  instead of too little, which is easier to diagnose and
          correct.
       The form of the substitute command that uses the n suffix  was  limited
       to  the  first  512  matches  in an early proposal. This limit has been
       removed because there is  no  reason  an  editor  processing  lines  of
       {LINE_MAX}  length should have this restriction. The command s/a/A/2047
       should be able to substitute the 2047th occurrence of a on a line.
       The b, t, and : commands are documented to ignore leading white  space,
       but  no mention is made of trailing white space. Historical implementa-
       tions of sed assigned different locations to the labels 'x' and "x "  .
       This  is  not useful, and leads to subtle programming errors, but it is
       historical practice, and changing it could theoretically break  working
       scripts.  Implementors are encouraged to provide warning messages about
       labels that are never used or jumps to labels that do not exist.
       Historically, the sed ! and } editing commands did not permit  multiple
       commands  on  a  single  line using a semicolon as a command delimiter.
       Implementations are permitted, but not required, to support this exten-
       sion.
FUTURE DIRECTIONS
       None.
SEE ALSO
       awk, ed, grep
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                              SED(1P)