sed命令工作原理及命令备忘

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Addresses Sed commands can be given with no addresses, in which case the command will be executed for all input lines; with one address, in which case the command will only be executed for input lines which match that address; or with two addresses, in which case the command will be executed for all input lines which match the inclusive range of lines starting from the first address and continuing to the second address. Three things to note about address ranges: the syntax is addr1,addr2 (i.e., the addresses are separated by a comma); the line which addr1 matched will always be accepted, even if addr2 selects an earlier line; and if addr2 is a regexp, it will not be tested against the line that addr1 matched. After the address (or address-range), and before the command, a ! may be inserted, which specifies that the command shall only be executed if the address (or address-range) does not match. The following address types are supported: number Match only the specified line number (which increments cumulatively across files, unless the -s option is specified on the command line). first~step Match every step'th line starting with line first. For example, ``sed -n 1~2p'' will print all the odd-numbered lines in the input stream, and the address 2~5 will match every fifth line, starting with the second. first can be zero; in this case, sed operates as if it were equal to step. (This is an extension.) $ Match the last line. /regexp/ Match lines matching the regular expression regexp. \cregexpc Match lines matching the regular expression regexp. The c may be any character. GNU sed also supports some special 2-address forms: 0,addr2 Start out in "matched first address" state, until addr2 is found. This is similar to 1,addr2, except that if addr2 matches the very first line of input the 0,addr2 form will be at the end of its range, whereas the 1,addr2 form will still be at the beginning of its range. This works only when addr2 is a regular expression. addr1,+N Will match addr1 and the N lines following addr1. addr1,~N Will match addr1 and the lines following addr1 until the next line whose input line number is a multiple of N.

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} The closing bracket of a { } block.

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= Print the current line number.a \text Append text, which has each embedded newline preceded by a backslash.i \text Insert text, which has each embedded newline preceded by a backslash.r filename Append text read from filename.R filename Append a line read from filename. Each invocation of the command reads a line from the file. This is a GNU extension.

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{ Begin a block of commands (end with a }).c \text Replace the selected lines with text, which has each embedded newline preceded by a backslash.d Delete pattern space. Start next cycle.D If pattern space contains no newline, start a normal new cycle as if the d command was issued. Otherwise, delete text in the pattern space up to the first newline, and restart cycle with the resul- tant pattern space, without reading a new line of input.h H Copy/append pattern space to hold space.g G Copy/append hold space to pattern space.n N Read/append the next line of input into the pattern space.p Print the current pattern space.P Print up to the first embedded newline of the current pattern space.s/regexp/replacement/ Attempt to match regexp against the pattern space. If successful, replace that portion matched with replacement. The replacement may contain the special character & to refer to that portion of the pattern space which matched, and the special escapes \1 through \9 to refer to the corresponding matching sub-expressions in the regexp.w filename Write the current pattern space to filename.W filename Write the first line of the current pattern space to filename. This is a GNU extension.x Exchange the contents of the hold and pattern spaces.y/source/dest/ Transliterate the characters in the pattern space which appear in source to the corresponding character in dest.