File: sed.info,  Node: Multiple commands syntax,  Prev: Extended Commands,  Up: sed scripts

3.8 Multiple commands syntax
============================

There are several methods to specify multiple commands in a ‘sed’
program.

   Using newlines is most natural when running a sed script from a file
(using the ‘-f’ option).

   On the command line, all ‘sed’ commands may be separated by newlines.
Alternatively, you may specify each command as an argument to an ‘-e’
option:

     $ seq 6 | sed '1d
     3d
     5d'
     2
     4
     6

     $ seq 6 | sed -e 1d -e 3d -e 5d
     2
     4
     6

   A semicolon (‘;’) may be used to separate most simple commands:

     $ seq 6 | sed '1d;3d;5d'
     2
     4
     6

   The ‘{’,‘}’,‘b’,‘t’,‘T’,‘:’ commands can be separated with a
semicolon (this is a non-portable GNU ‘sed’ extension).

     $ seq 4 | sed '{1d;3d}'
     2
     4

     $ seq 6 | sed '{1d;3d};5d'
     2
     4
     6

   Labels used in ‘b’,‘t’,‘T’,‘:’ commands are read until a semicolon.
Leading and trailing whitespace is ignored.  In the examples below the
label is ‘x’.  The first example works with GNU ‘sed’.  The second is a
portable equivalent.  For more information about branching and labels
*note Branching and flow control::.

     $ seq 3 | sed '/1/b x ; s/^/=/ ; :x ; 3d'
     1
     =2

     $ seq 3 | sed -e '/1/bx' -e 's/^/=/' -e ':x' -e '3d'
     1
     =2

3.8.1 Commands Requiring a newline
----------------------------------

The following commands cannot be separated by a semicolon and require a
newline:

‘a’,‘c’,‘i’ (append/change/insert)

     All characters following ‘a’,‘c’,‘i’ commands are taken as the text
     to append/change/insert.  Using a semicolon leads to undesirable
     results:

          $ seq 2 | sed '1aHello ; 2d'
          1
          Hello ; 2d
          2

     Separate the commands using ‘-e’ or a newline:

          $ seq 2 | sed -e 1aHello -e 2d
          1
          Hello

          $ seq 2 | sed '1aHello
          2d'
          1
          Hello

     Note that specifying the text to add (‘Hello’) immediately after
     ‘a’,‘c’,‘i’ is itself a GNU ‘sed’ extension.  A portable,
     POSIX-compliant alternative is:

          $ seq 2 | sed '1a\
          Hello
          2d'
          1
          Hello

‘#’ (comment)

     All characters following ‘#’ until the next newline are ignored.

          $ seq 3 | sed '# this is a comment ; 2d'
          1
          2
          3


          $ seq 3 | sed '# this is a comment
          2d'
          1
          3

‘r’,‘R’,‘w’,‘W’ (reading and writing files)

     The ‘r’,‘R’,‘w’,‘W’ commands parse the filename until end of the
     line.  If whitespace, comments or semicolons are found, they will
     be included in the filename, leading to unexpected results:

          $ seq 2 | sed '1w hello.txt ; 2d'
          1
          2

          $ ls -log
          total 4
          -rw-rw-r-- 1 2 Jan 23 23:03 hello.txt ; 2d

          $ cat 'hello.txt ; 2d'
          1

     Note that ‘sed’ silently ignores read/write errors in
     ‘r’,‘R’,‘w’,‘W’ commands (such as missing files).  In the following
     example, ‘sed’ tries to read a file named ‘‘hello.txt ; N’’.  The
     file is missing, and the error is silently ignored:

          $ echo x | sed '1rhello.txt ; N'
          x

‘e’ (command execution)

     Any characters following the ‘e’ command until the end of the line
     will be sent to the shell.  If whitespace, comments or semicolons
     are found, they will be included in the shell command, leading to
     unexpected results:

          $ echo a | sed '1e touch foo#bar'
          a

          $ ls -1
          foo#bar

          $ echo a | sed '1e touch foo ; s/a/b/'
          sh: 1: s/a/b/: not found
          a

‘s///[we]’ (substitute with ‘e’ or ‘w’ flags)

     In a substitution command, the ‘w’ flag writes the substitution
     result to a file, and the ‘e’ flag executes the substitution result
     as a shell command.  As with the ‘r/R/w/W/e’ commands, these must
     be terminated with a newline.  If whitespace, comments or
     semicolons are found, they will be included in the shell command or
     filename, leading to unexpected results:

          $ echo a | sed 's/a/b/w1.txt#foo'
          b

          $ ls -1
          1.txt#foo