sed(1)sed(1)NAMEsed - Stream editor
SYNOPSISsed [-n] script [file...]
sed [-n] [-e script]... [-f script_file...]... [file...]
The sed utility is a stream editor that reads one or more text files,
makes editing changes according to a script of editing commands and
writes the results to standard output.
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
sed: XCU5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
OPTIONS
Add the editing commands specified by the string script to the end of
the script of editing commands. If you are using just one -e option
and no -f option, you can omit the -e option and include the single
script on the command line as an argument to sed. Uses script_file as
the source of the edit script. The script_file is a set of editing
commands to be applied to file. Suppresses all information normally
written to standard output.
The order of presentation of the -e and -f options is significant.
OPERANDS
Use the string script as an editing script. See the description of the
-e option. The path name of a file to be edited. If multiple file op‐
erands are specified, all files are read and concatenated before edit‐
ing begins.
If no file file operand is specified, standard input is read.
DESCRIPTION
The sed command includes many features for selecting lines to be modi‐
fied and making changes only to the selected lines.
The sed command uses two work spaces for holding the line being modi‐
fied: the pattern space, where the selected line is held, and the hold
space, where a line can be stored temporarily.
An edit script consists of individual subcommands, each one on a sepa‐
rate line. The general form of sed subcommands is as follows:
[address_range] function [modifier ...]
The sed command processes each input file by reading an input line into
a pattern space, sequentially applying all sed subcommands in sequence
whose addresses select that line, and writing the pattern space to
standard output. It then clears the pattern space and repeats this
process for each line in the input file. Some of the subcommands use a
hold space to save all or part of the pattern space for subsequent
retrieval.
[Tru64 UNIX] If you do not specify an argument to the sed command, the
sed usage string is displayed.
When a command includes an address, either a line number or a search
pattern, only the addressed line or lines are affected by the command.
Otherwise, the command is applied to all lines.
An address is either a decimal line number, a $, which addresses the
last line of input, or a context address. A context address is a basic
regular expression (BRE) as described for grep, except that you can
select the character delimiter for patterns. The general form of the
expression is as follows: \?pattern?
The ? represents a character delimiter you select. The backslash (\)
is required when you select a delimiter other than the default slash
(/) character. This delimiter cannot be a 2-byte international charac‐
ter support extended character.
The default form for the pattern is as follows: /pattern/
In a context address, the construction \cexpressionc, where c is any
character other than a backslash (\) or the newline character, is iden‐
tical to /expression/. If the character designated by c appears fol‐
lowing a \ (backslash), then it is considered to be that literal char‐
acter, which does not terminate the RE. For example, in the context
address \xabc\xdefx, the second x stands for itself, so that the regu‐
lar expression is abcxdef. The sequence \n matches a newline character
in the pattern space, except the terminating new line. A dot (.)
matches any character except a terminating newline character. That is,
unlike grep, which cannot match a newline character in the middle of a
line, sed can match a newline character in the pattern space.
Certain commands allow you to specify one line or a range of lines to
which the command applies. These commands are called addressed com‐
mands. The following rules apply to addressed commands: A command line
with no address selects every line. A command line with one address,
expressed in context form, selects each line that matches the address.
A command line with two addresses separated by a comma (,) or semicolon
(;) selects the entire range from the first line that matches the first
address through the next line that matches the second. (If the second
address is a number less than or equal to the line number first
selected, only one line is selected.) Thereafter, the process is
repeated, looking again for the first address.
Subcommands
Backslashes in text are treated like backslashes in the replacement
string of an s command and can be used to protect initial spaces and
tabs against the stripping that is done on every script line.
The text argument accompanying the a\, c\, and i\ commands can continue
onto more than one line, provided all lines but the last end with a \
(backslash) to quote the newline character.
The read_file and write_file arguments must end the command line and
must be preceded by exactly one space. Each write_file is created
before processing begins.
[Tru64 UNIX] The sed command can process up to 999 commands in a file.
In the following list of subcommands, the maximum number of permissible
addresses for each subcommand is indicated in parentheses. The sed
script subcommands are as follows: Groups subcommands enclosed in { }
(braces). The { (left brace) can be preceded by spaces and can be fol‐
lowed by spaces or tabs. The list of subcommands must be separated by
newline characters. The subcommands can also be preceded by spaces or
tabs. The terminating } (right brace) must be preceded by a newline
character and then zero or more spaces. Places text on the output
before reading the next input line.
The total number of a and/or r subcommands should not exceed 20.
Branches to the : command bearing the label. If label is empty,
it branches to the end of the script. The labels should not
exceed 8 characters in length. Label names should not be dupli‐
cated. The maximum number of labels allowed in the sed script
is 50. Deletes the pattern space. With a 0 or 1 address or at
the end of a 2-address range, places text on the output. Then
it starts the next cycle. Deletes the pattern space, then
starts the next cycle. Deletes the initial segment of the pat‐
tern space through the first newline character. Then it starts
the next cycle. Replaces the contents of the pattern space with
the contents of the hold space. Appends the contents of the
hold space to the pattern space. Replaces the contents of the
hold space with the contents of the pattern space. Appends the
contents of the pattern space to the hold space. Writes text to
standard output before reading the next line into the pattern
space. Writes the pattern space to standard output, showing
nonprinting characters as 3-digit octal values. Long lines are
folded, with the point of folding indicated by <Back‐
slash><Return>. The end of each line is marked with a $.
Certain characters are shown as escape sequences as follows:
Backslash Alert Backspace Formfeed Newline Carriage-return Tab
Vertical tab Writes the pattern space to standard output. It
replaces the pattern space with the next line of input. Appends
the next line of input to the pattern space with an embedded
newline character. (The current line number changes.) You can
use this to search for patterns that are split onto two lines.
Writes the pattern space to standard output. Writes the initial
segment of the pattern space through the first newline character
to standard output. Branches to the end of the script. It does
not start a new cycle. Reads the contents of read_file. It
places contents on the output before reading the next input
line.
The total number of a and/or r subcommands should not exceed 20.
Substitutes the replacement string for the first occurrence of
the pattern in the pattern space. Any character that is entered
after the s command can substitute for the / (slash) separator,
except \ (backslash) and the newline character. Within the reg‐
ular expression and replacement string, the delimiter can appear
as a literal if it is preceded by a \ (backslash).
An & (ampersand) appearing in the replacement string is replaced
by the string matching the RE. The special meaning of & in this
context can be suppressed by preceding it with a \ (backslash).
The characters \n, where n is a digit, are replaced by the text
matched by the corresponding backreference expression.
A line can be split by substituting a newline character into it.
You must escape the newline character in the replacement string
by preceding it with a \ backslash. A substitution is consid‐
ered to have been performed even if the replacement string is
identical to the string that it replaces.
You can add zero or more of the following flags: Where n is
1-512, substitutes replacement for the nth occurrence of pattern
on each addressed line, rather than for the first occurrence.
Substitutes replacement for all nonoverlapping instances of pat‐
tern on each addressed line, rather than for just the first one
(or for the one specified by n). Writes the pattern space to
standard output if a replacement was made.
[SVR4] If the environment variable CMD_ENV is set either to
SVR4 or svr4, writes the substituted pattern space to standard
output only once at the end of the script, unless the -n option
is specified. Writes the pattern space to write_file if a
replacement was made. Appends the pattern space to write_file.
If write_file was not already created by a previous write by
this sed script, sed creates it. Each write_file is created
before processing begins.
A maximum number of 10 files can be created by sed. Branches to
:label in the script file if any substitutions were made since
the most recent reading of an input line execution of a t sub‐
command. If you do not specify label, control transfers to the
end of the script. Appends the pattern space to write_file.
Exchanges the contents of the pattern space and the hold space.
Replaces all occurrences of characters in pattern1 with the cor‐
responding characters from pattern2. The byte lengths of pat‐
tern1 and pattern2 must be equal. Applies the specified sed
subcommand only to lines not selected by the address or
addresses. This script entry simply marks a branch point to be
referenced by the b and t commands. This label can be any
sequence of eight or fewer bytes. Writes the current line num‐
ber to standard output as a line. Groups subcommands enclosed
in { } (braces). Ignores an empty command. If a # (number
sign) appears as the first character on the first line of a
script file, that entire line is treated as a comment, with one
exception. If the character after the # is an n, the default
output is suppressed. The rest of the line after the #n is
ignored. A script must contain at least one noncomment line.
RESTRICTIONS
[Tru64 UNIX] The h subcommand for sed does not work properly. When
you use the h subcommand to place text into the hold area, only the
last line of the specified text is saved. You can use the H subcommand
to append text to the hold area. The H subcommand and all others deal‐
ing with the hold area work correctly.
EXIT STATUS
The following exit values are returned: Successful completion. An
error occurred.
EXAMPLES
To perform a global change, enter: sed "s/happy/enchanted/g" chap1
>chap1.new
This replaces each occurrence of happy found in the file chap1
with enchanted, and puts the edited version in a separate file
named chap1.new. The g at the end of the s subcommand tells sed
to make as many substitutions as possible on each line. Without
the g, sed replaces only the first happy on a line.
The sed stream editor operates as a filter. It reads text from
standard input or from the files named on the command line
(chap1 in this example), modifies this text, and writes it to
standard output. Unlike most editors, it does not replace the
original file. This makes sed a powerful command when used in
pipelines. To use sed as a filter in a pipeline (sh only),
enter: pr chap2 | sed "s/Page *[0-9]*$/(&)/" | print
This encloses the page numbers in parentheses before printing
chap2. The pr command puts a heading and page number at the top
of each page, then sed puts the page numbers in parentheses, and
the print command prints the edited listing.
The sed pattern /Page *[0-9]*$/ matches page numbers that appear
at the end of a line. The s subcommand changes this to (&),
where the & stands for the pattern that was matched (for exam‐
ple, Page 5). To display selected lines of a file, enter: sed-n "/food/p" chap3
This displays each line in chap3 that contains the word food.
Normally, sed copies every line to standard output after it is
edited. The -n option stops sed from doing this. You then use
subcommands like p to write specific parts of the text. Without
the -n, this example displays all the lines in chap3, and it
shows each line containing food twice. To perform complex edit‐
ing, enter: sed-f script.sed chap4 >chap4.new
It is always a good idea to create a sed script file when you
want to do anything complex. You can then test and modify your
script before using it. You can also reuse your script to edit
other files. Create the script file with an interactive text
editor. A sample sed script follows:
:join /\\$/{N s/\\\n// b join }
This sed script joins each line that ends with a \ (backslash)
to the line that follows it. First, the pattern /\\$/ selects a
line that ends with a \ for the group of commands enclosed in {
}. The N subcommand then appends the next line, embedding a
newline character. The s/\\\n// deletes the \ (backslash) and
embedded newline character. Finally, b join branches back to
the label :join to check for a \ (backslash) at the end of the
newly joined line. Without the branch, sed writes the joined
line and reads the next one before checking for a second \ char‐
acter.
The N subcommand causes sed to stop immediately if there are no
more lines of input (that is, if N reads the End-of-File charac‐
ter). It does not copy the pattern space to standard output
before stopping. This means that if the last line of the input
ends with a \ (backslash) character, then it is not copied to
the output.
ENVIRONMENT VARIABLES
The following environment variables affect the execution of sed: Pro‐
vides a default value for the internationalization variables that are
unset or null. If LANG is unset or null, the corresponding value from
the default locale is used. If any of the internationalization vari‐
ables contain an invalid setting, the utility behaves as if none of the
variables had been defined. If set to a non-empty string value, over‐
rides the values of all the other internationalization variables.
Determines 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 the behavior of character classes
within regular expressions. Determines the locale for the format and
contents of diagnostic messages written to standard error. Determines
the location of message catalogues for the processing of LC_MESSAGES.
SEE ALSO
Commands: awk(1), ed(1), grep(1), vi(1)
Standards: standards(5)
Programming Support Tools
sed(1)
