Linux and UNIX Man Pages

Test Your Knowledge in Computers #131
Difficulty: Easy
UNIX certification is based on the 'Single Unix Specification' which is an extension of IEEE 1003 (POSIX).
True or False?
Linux & Unix Commands - Search Man Pages

sed(1) [v7 man page]

SED(1)							      General Commands Manual							    SED(1)

NAME
sed - stream editor SYNOPSIS
sed [ -n ] [ -e script ] [ -f sfile ] [ file ] ... DESCRIPTION
Sed copies the named files (standard input default) to the standard output, edited according to a script of commands. 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's, the flag -e may be omitted. The -n option suppresses the default output. A script consists of editing commands, 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. An address is either a decimal number that counts input lines cumulatively across files, a `$' that addresses the last line of input, or a context address, `/regular expression/', in the style of ed(1) modified thus: The escape sequence ` ' matches a newline embedded in 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 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 non-selected 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. An argument denoted text consists of one or more lines, all but the last of which end with `' to hide the newline. 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. An argument denoted rfile or wfile must terminate the command line and must be preceded by exactly one blank. Each wfile is created before processing begins. There can be at most 10 distinct wfile arguments. (1)a text Append. Place text on the output before reading the next input line. (2)b label Branch to the `:' command bearing the label. If label is empty, branch to the end of the script. (2)c text Change. Delete the pattern space. With 0 or 1 address or at the end of a 2-address range, place text on the output. Start the next cycle. (2)d Delete the pattern space. Start the next cycle. (2)D Delete the initial segment of the pattern space through the first newline. Start the next cycle. (2)g Replace the contents of the pattern space by the contents of the hold space. (2)G Append the contents of the hold space to the pattern space. (2)h Replace the contents of the hold space by the contents of the pattern space. (2)H Append the contents of the pattern space to the hold space. (1)i text Insert. Place text on the standard output. (2)l List the pattern space on the standard output in an unambiguous form. Non-printing characters are spelled in two digit ascii, and long lines are folded. (2)n Copy the pattern space to the standard output. Replace the pattern space with the next line of input. (2)N Append the next line of input to the pattern space with an embedded newline. (The current line number changes.) (2)p Print. Copy the pattern space to the standard output. (2)P Copy the initial segment of the pattern space through the first newline to the standard output. (1)q Quit. Branch to the end of the script. Do not start a new cycle. (2)r rfile Read the contents of rfile. Place them on the output before reading the next input line. (2)s/regular expression/replacement/flags Substitute the replacement string for instances of the regular expression in the pattern space. Any character may be used instead of `/'. For a fuller description see ed(1). Flags is zero or more of g Global. Substitute for all nonoverlapping instances of the regular expression rather than just the first one. p Print the pattern space if a replacement was made. w wfile Write. Append the pattern space to wfile if a replacement was made. (2)t label Test. Branch to the `:' command bearing the label if any substitutions have been made since the most recent reading of an input line or execution of a `t'. If label is empty, branch to the end of the script. (2)w wfile Write. Append the pattern space to wfile. (2)x Exchange the contents of the pattern and hold spaces. (2)y/string1/string2/ Transform. Replace all occurrences of characters in string1 with the corresponding character in string2. The lengths of string1 and string2 must be equal. (2)! function Don't. Apply 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' commands to branch to. (1)= Place the current line number on the standard output as a line. (2){ Execute the following commands through a matching `}' only when the pattern space is selected. (0) An empty command is ignored. SEE ALSO
ed(1), grep(1), awk(1) SED(1)

Featured Tech Videos