sed(C) 06 January 1993 sed(C) Name sed - invoke the stream editor Syntax sed [ -n ] [ -e script ] [ -f sfile ] [ files ] Description The sed command copies the named files (standard input default) to the standard output, edited according to a script of commands. The -e option causes the script to be read literally from the next argument, which is usually quoted to protect it from the shell. The -f option causes the script to be taken from file sfile; these options accumulate. If there is just one -e option and no -f options, the flag -e may be omitted. The -n option suppresses the default output. A script consists of editing com- mands, one per line, of the following form: [ address [ , address ] ] function [ arguments ] In normal operation, sed cyclically copies a line of input into a pattern space (unless there is something left after a D command), applies in sequence all commands whose addresses select that pattern space, and at the end of the script copies the pattern space to the standard output (except under -n) and deletes the pattern space. A semicolon (;) can be used as a command delimiter. Some of the commands use a hold space to save all or part of the pattern space for subsequent retrieval. An address is either a decimal number that counts input lines cumula- tively across files, a ``$'' that addresses the last line of input, or a context address, that is, a /regular expression/ in the style of ed(C) modified as follows: + In a context address, the construction \?regular expression?, where ``?'' is any character, is identical to /regular expression/. Note that in the context address \xabc\xdefx, the second x stands for itself, so that the standard expression is abcxdef. + The escape sequence \n matches a newline embedded in the pattern space. + A dot (.) matches any character except the terminal newline of the pattern space. + A command line with no addresses selects every pattern space. + A command line with one address selects each pattern space that matches the address. + A command line with two addresses separated by a comma selects 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 is selected.) Thereafter, the process is repeated, looking again for the first address. Editing commands can be applied only to nonselected pattern spaces by use of the negation function ``!'' (below). In the following list of functions, the maximum number of permissible addresses for each function is indicated in parentheses. The text argument consists of one or more lines, all but the last of which end with backslashes to hide the newlines. Backslashes in text are treated like backslashes in the replacement string of an s command, and may be used to protect initial blanks and tabs against the stripping that is done on every script line. The rfile or wfile argument must terminate the command line and must be preceded by one blank. Each wfile is created before processing begins. There can be at most 10 distinct wfile argu- ments. (1) a\ text Appends text, placing it on the output before reading the next input line. (2) b label Branches to the : command bearing the label. If label is empty, branches to the end of the script. (2) c\ text Changes text by deleting the pattern space and then appending text. With 0 or 1 address or at the end of a 2-address range, places text on the output and starts the next cycle. (2) d Deletes the pattern space and starts the next cycle. (2) D Deletes the initial segment of the pattern space through the first newline and starts the next cycle. (2) g Replaces the contents of the pattern space with the contents of the hold space. (2) G Appends the contents of the hold space to the pattern space. (2) h Replaces the contents of the hold space with the contents of the pattern space. (2) H Appends the contents of the pattern space to the hold space. (1) i\ text Insert. Places text on the standard output. (2) l Lists the pattern space on the standard output with nonprinting characters spelled in two-digit ASCII and long lines folded. (2) n Copies the pattern space to the standard output. Replaces the pattern space with the next line of input. (2) N Appends the next line of input to the pattern space with an embedded newline. (The current line number changes.) (2) p Prints (copies) the pattern space on the standard output. (2) P Prints (copies) the initial segment of the pattern space through the first newline to the standard output. (1) q Quits sed by branching to the end of the script. No new cycle is started. (2) r rfile Reads the contents of rfile and places them on the output before reading the next input line. (2) s /regular expression/replacement/flags Substitutes the replacement string for instances of the regular expression in the pattern space. Any character may be used instead of ``/''. For a more detailed description, see ed(C). Flags is zero or more of: n n=1-512. Substitute for just the nth occurrence of the regular expression. g Globally substitutes for all non-overlapping instances of the regular expression rather than just the first one. p Prints the pattern space if a replacement was made. w wfile Writes the pattern space to wfile if a replacement was made. (2) t label Branches to the colon (:) command bearing label if any substi- tutions have been made since the most recent reading of an input line or execution of a t command. If label is empty, t branches to the end of the script. (2) w wfile Writes the pattern space to wfile. (2) x Exchanges the contents of the pattern and hold spaces. (2) y /string1/string2/ Replaces all occurrences of characters in string1 with the cor- responding characters in string2. The lengths of string1 and string2 must be equal. (2) ! function Applies the function (or group, if function is ``{'') only to lines NOT selected by the address(es). (0) : label This command does nothing; it bears a label for b and t com- mands to branch to. (1) = Places the current line number on the standard output as a line. (2) { Executes the following commands through a matching ``}'' only when the pattern space is selected. (0) An empty command is ignored. Examples The following examples assume the use of sh or ksh. The most common use of sed is to edit a file from within a shell script. In this example, every occurrence of the string ``sysman'' in the file infile is replaced by ``System Manager''. A temporary file TMP is used to hold the intermediate result of the edit: TMP=/usr/tmp/tmpfile_$$ sed -e 's/sysman/System Manager/g' < infile > $TMP mv $TMP infile sed can be used to strip all lines from a file which do not contain a certain string. In this example, all lines in the file infile which start with a hash ``#'' are echoed to the screen: sed -e '/^#/!d' < infile If several editing commands must be carried out on a file, but the param- eters for the edit are to be supplied by the user, then a document can be used to build a temporary edit script for sed to use. The following exam- ple removes all occurrences of the strings given as arguments to the script from the file infile. The name of the temporary script is held by the variable SCRIPT: SCRIPT=/usr/tmp/script_$$ for name in $* do cat >> $SCRIPT <<! s/${name}//g ! done TMPFILE=/usr/tmp/tmpfile_$$ sed -f $SCRIPT < infile > $TMPFILE mv $TMPFILE infile rm $SCRIPT Another use of sed is to process the output from other commands. Here the ps command is filtered using sed to report the status of all processes other than those owned by the super user: ps -ef | sed -e '/^[<Space><Tab>]*root/d' See also awk(C), ed(C) and grep(C). Notes This command is explained in detail in the User's Guide. Standards conformance sed is conformant with: AT&T SVID Issue 2; and X/Open Portability Guide, Issue 3, 1989.