A single command may be specified as the first argument to sed . Multiple commands may be specified by using the -e or -f options. All commands are applied to the input in the order they are specified regardless of their origin.
The following options are available:
The form of a sed command is as follows:
Whitespace may be inserted before the first address and the function portions of the command.
Normally, sed cyclically copies a line of input, not including its terminating newline character, into a "pattern space" , (unless there is something left after a "D" function), applies all of the commands with addresses that select that pattern space, copies the pattern space to the standard output, appending a newline, and deletes the pattern space.
Some of the functions use a "hold space" to save all or part of the pattern space for subsequent retrieval.
A command line with no addresses selects every pattern space.
A command line with one address selects all of the pattern spaces that match 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 that line is selected.) Starting at the first line following the selected range, sed starts looking again for the first address.
Editing commands can be applied to non-selected pattern spaces by use of the exclamation character ( "!" ) function.
One special feature of sed regular expressions is that they can default to the last regular expression used. If a regular expression is empty, i.e. just the delimiter characters are specified, the last regular expression encountered is used instead. The last regular expression is defined as the last regular expression used as part of an address or substitute command, and at run-time, not compile-time. For example, the command "/abc/s//XXX/" will substitute "XXX" for the pattern "abc ."
The argument text consists of one or more lines. To embed a newline in the text, precede it with a backslash. Other backslashes in text are deleted and the following character taken literally.
The "r" and "w" functions take an optional file parameter, which should be separated from the function letter by white space. Each file given as an argument to sed is created (or its contents truncated) before any input processing begins.
The "b ," "r ," "s ," "t ," "w ," "y ," "! ," and ":" functions all accept additional arguments. The following synopses indicate which arguments have to be separated from the function letters by white space characters.
Two of the functions take a function-list. This is a list of sed functions separated by newlines, as follows:
The "{" can be preceded by white space and can be followed by white space. The function can be preceded by white space. The terminating "}" must be preceded by a newline or optional white space.
backslash \ alert \a form-feed \f newline \n carriage-return \r tab \t vertical tab \v
Nonprintable characters are written as three-digit octal numbers (with a preceding backslash) for each byte in the character (most significant byte first). Long lines are folded, with the point of folding indicated by displaying a backslash followed by a newline. The end of each line is marked with a "$ ."
An ampersand ( "&" ) appearing in the replacement is replaced by the string matching the RE. The special meaning of "&" in this context can be suppressed by preceding it by a backslash. The string "\# ," where "#" is a digit, is replaced by the text matched by the corresponding backreference expression (see re_format (7) ).
A line can be split by substituting a newline character into it. To specify a newline character in the replacement string, precede it with a backslash.
The value of flags in the substitute function is zero or more of the following:
The sed utility exits 0 on success and >0 if an error occurs.