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sed

sed

sed Stream editor.
sed [-an] <command> [<file> ...]

sed [-an] [-e <command>] [-f <command_file>] [<file>]

sed reads one or more text files, or standard input if no file is specified, makes editing changes according to a single command specified by <command> or by using the -e or -f options. The input is then written to standard output. All commands are applied to the input in the order they are specified, regardless of their origin.
-a By default, the files listed as parameters for the w functions are created or truncated before any processing begins. This option causes sed to delay opening each file until a command containing the related w function is applied to a line of input.
-n By default, each line of input is echoed to the standard output after all the commands have been applied to it. This option suppresses the default output behavior.
-e <command> Appends editing commands specified by the <command> argument to the list of commands.
-f <command_file> Appends editing commands found in the file <command_file> to the list of commands. The editing commands should be listed one per line.
The form of a sed command is as follows:
[address[,address]]function[arguments]

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 the D function), applies all the commands with addresses that select that pattern space, copies the resulting pattern space to the standard output (except if -n is used), appends 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.
Addresses
An address is not required, but if specified, must be a number that counts input lines cumulatively across input files, a $ that addresses the last line of input, or a context address that consists of a regular expression preceded and followed by a delimiter.
A command line with no addresses selects every pattern space.
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 of the selected range, sed starts looking again for the first address.
Editing commands can be applied to nonselected pattern spaces by use of ! , the negation function.
Regular Expressions
sed regular expressions are basic regular expressions (see regex (3)) with these additions:
1. In context addresses, any character other than \ or the newline character may be used to delimit a regular expression by prefixing the first use of that delimiter with \. Also, putting \ before the delimiting character causes the character to be treated literally, which does not terminate the regular expression. For example, in the context address \xabc\xdefx, the second x stands for itself, so that the regular expression is abcxdef.
2. The escape sequence \n matches a newline character embedded in the pattern space. A literal newline character must not be used in the regular expression of a context address or in the substitute command.
One special feature of sed regular expressions is that they can default to the last regular expression used. If a regular expression is empty (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/ substitutes XXX for the pattern abc.
Functions
In the following list of commands, the maximum number of permissible addresses for each command is indicated by [0addr], [1addr], or [2addr], representing zero, one, or two addresses.
The argument <text> consists of one or more lines. To embed a newline in the text, precede it with a \. 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 whitespace.
Two of the functions take a function list. This is a list of sed functions separated by newlines, as follows:
{  function
  function
  . . .
  }

The { can be preceded by whitespace and can be followed by whitespace. The function can be preceded by whitespace. The terminating } must be preceded by a newline or optional white space.
The following lists the functions:
Maximum Number of Addresses Command Description
[2addr] {<function_list>} Executions <function-list> | only when the pattern space is selected.
[1addr] a\  
<text>  Writes <text> to standard output immediately before each attempt to read a line of output, whether by executing the N function or beginning a new cycle.
[2addr] b <label> Branches to the : function with the specified label. If the label is not specified, it branches to the end of the script.
[2addr] c\  
<text>  Change. Deletes the pattern space. With zero or one address or at the end of a two-address range, <text> is written to standard output.
[2addr] d Deletes the pattern space and starts the next cycle.
[2addr] D Deletes the initial segment of the pattern space through the first newline character and starts the next cycle.
[2addr] g Replaces the contents of the pattern space with the contents of the hold space.
[2addr] G Appends a newline character followed by the contents of the hold space to the pattern space.
[2addr] h Replaces the contents of the hold space with the contents of the pattern space.
[2addr] H Appends a newline character followed by the contents of the pattern space.
[1addr] i\  
<text>  Insert. Writes <text> to the standard output.
[2addr] l Writes the pattern space to the standard output in a visually unambiguous form. The form is as follows:
Backslash  \\
Alert  \a
Form-feed  \f
Newline  \n
Carriage return  \r
Tab  \t
Vertical tab  \v
  Nonprinting 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 $.
[2addr] n Writes the pattern space to the standard output if the default output has not been suppressed, and replaces the pattern space with the next line of input.
[2addr] N Appends the next line of input to the pattern space, using an embedded newline character to separate the appended material from the original contents. (The current line number changes.)
[2addr] p Writes the pattern space to standard output.
[2addr] P Writes the pattern space, up to the first newline character, to the standard output.
[1addr] q Branches to the end of the script and quits without starting a new cycle.
[1addr] r <file> Copies the contents of <file> to the standard output immediately before the next attempt to read a line of input. If <file> cannot be read for any reason, it is silently ignored and no error condition is set.
[2addr] t <label> Test. Branches to the : function bearing the <label> if any substitutions have been made since the most recent reading of an input line or execution of a t function. If no label is specified, branches to the end of the script.
[2addr] w <file> Appends the pattern space to the <file>.
[2addr] x Exchanges the contents of the pattern and hold spaces.
[2addr] !<function>  
!<function_list>  Applies the <function> or <function_list> only to the lines that are not selected by the address(es).
[0addr] :<label> This function does nothing. It bears a <label> to which the b and t commands may branch.
[1addr] = Writes the line number to the standard output followed by a newline character.
[0addr]  Empty lines are ignored.
[0addr] # # and the remainder of the line are ignored (treated as a comment), with the single exception that if the first two characters in the file are #n, the default output is suppressed. This is the same as specifying the -n option in the command line.
[2addr] y/<string1>/<string2>  
  Replaces all occurrences of the characters in <string1> in the pattern space with the corresponding characters from <string2>. Any character other than a backslash or newline can be used instead of a slash to delimit the strings. Within <string1> and <string2>, a backslash followed by any character other than a newline is that literal character, and a backslash followed by an n is replaced by a newline character.
[2addr] s/<regular expression>/ <replacement>/<flags>  
  Substitutes the replacement string for the first instance of the regular expression in the pattern space. Any character other than the back- slash or newline can be used instead of a slash to delimit the regular expression. Within the regular expression and the replacement, the regular expression delimiter itself can be used as a literal character if it is preceded by a backslash.
  An ampersand appearing in the replacement is replaced by the string matching the regular expression. The special meaning of the & in this context can be suppressed by preceding it with a backslash. The string \# where # is a digit is replaced by the text matched by the corresponding back reference 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:
  0 … 9 Makes the substitution only for the nth occurrence of the regular expression in the pattern space.
  g Makes the substitution for all nonoverlapping matches of the regular expression, not just the first one.
  p Writes the pattern space to standard output if a replacement was made. If the replacement string is identical to that which it replaces, it is still considered to have been a replacement.
  w <file> Appends the pattern space to <file> if a replacment was made. If the replacement string is identical to that which it replaces, it is still considered to have been a replacement.



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