sed 用法

linux之sed用法

sed是一个很好的文件处理工具，本身是一个管道命令，主要是以行为单位进行处理，可以将数据行进行替换、删除、新增、选取等特定工作，下面先了解一下sed的用法
sed命令行格式为：
         sed [-nefri] ‘command’ 输入文本        

常用选项：
        -n∶使用安静(silent)模式。在一般 sed 的用法中，所有来自 STDIN的资料一般都会被列出到萤幕上。但如果加上 -n 参数后，则只有经过sed 特殊处理的那一行(或者动作)才会被列出来。
        -e∶直接在指令列模式上进行 sed 的动作编辑；
        -f∶直接将 sed 的动作写在一个档案内， -f filename 则可以执行 filename 内的sed 动作；
        -r∶sed 的动作支援的是延伸型正规表示法的语法。(预设是基础正规表示法语法)
        -i∶直接修改读取的档案内容，而不是由萤幕输出。       

常用命令：
        a   ∶新增， a 的后面可以接字串，而这些字串会在新的一行出现(目前的下一行)～
        c   ∶取代， c 的后面可以接字串，这些字串可以取代 n1,n2 之间的行！
        d   ∶删除，因为是删除啊，所以 d 后面通常不接任何咚咚；
         i   ∶插入， i 的后面可以接字串，而这些字串会在新的一行出现(目前的上一行)；
         p  ∶列印，亦即将某个选择的资料印出。通常 p 会与参数 sed -n 一起运作～
         s  ∶取代，可以直接进行取代的工作哩！通常这个 s 的动作可以搭配正规表示法！例如 1,20s/old/new/g 就是啦！

举例：（假设我们有一文件名为ab）
     删除某行
     [root@localhost ruby] # sed '1d' ab              #删除第一行 
     [root@localhost ruby] # sed '$d' ab              #删除最后一行
     [root@localhost ruby] # sed '1,2d' ab           #删除第一行到第二行
     [root@localhost ruby] # sed '2,$d' ab           #删除第二行到最后一行

　　显示某行
.    [root@localhost ruby] # sed -n '1p' ab           #显示第一行 
     [root@localhost ruby] # sed -n '$p' ab           #显示最后一行
     [root@localhost ruby] # sed -n '1,2p' ab        #显示第一行到第二行
     [root@localhost ruby] # sed -n '2,$p' ab        #显示第二行到最后一行

　　使用模式进行查询
     [root@localhost ruby] # sed -n '/ruby/p' ab    #查询包括关键字ruby所在所有行
     [root@localhost ruby] # sed -n '/\$/p' ab        #查询包括关键字$所在所有行，使用反斜线\屏蔽特殊含义

　　增加一行或多行字符串
     [root@localhost ruby]# cat ab
     Hello!
     ruby is me,welcome to my blog.
     end
     [root@localhost ruby] # sed '1a drink tea' ab  #第一行后增加字符串"drink tea"
     Hello!
     drink tea
     ruby is me,welcome to my blog. 
     end
     [root@localhost ruby] # sed '1,3a drink tea' ab #第一行到第三行后增加字符串"drink tea"
     Hello!
     drink tea
     ruby is me,welcome to my blog.
     drink tea
     end
     drink tea
     [root@localhost ruby] # sed '1a drink tea\nor coffee' ab   #第一行后增加多行，使用换行符\n
     Hello!
     drink tea
     or coffee
     ruby is me,welcome to my blog.
     end

　　代替一行或多行
     [root@localhost ruby] # sed '1c Hi' ab                #第一行代替为Hi
     Hi
     ruby is me,welcome to my blog.
     end
     [root@localhost ruby] # sed '1,2c Hi' ab             #第一行到第二行代替为Hi
     Hi
     end

　　替换一行中的某部分
　　格式：sed 's/要替换的字符串/新的字符串/g'   （要替换的字符串可以用正则表达式）
     [root@localhost ruby] # sed -n '/ruby/p' ab | sed 's/ruby/bird/g'    #替换ruby为bird
　  [root@localhost ruby] # sed -n '/ruby/p' ab | sed 's/ruby//g'        #删除ruby

     插入
     [root@localhost ruby] # sed -i '$a bye' ab         #在文件ab中最后一行直接输入"bye"
     [root@localhost ruby]# cat ab
     Hello!
     ruby is me,welcome to my blog.
     end
     bye

——————————————————————————————————————————————————————

SED                       BSD General Commands Manual                   

NAME

     sed -- stream editor

SYNOPSIS

     sed [-Ealn] command [file ...]

     sed [-Ealn] [-e command] [-f command_file] [-i extension] [file ...]

DESCRIPTION

     The sed utility reads the specified files, or the standard input if no files are specified, modifying

     the input as specified by a list of commands.  The input is then written to the standard output.

     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:

     -E      Interpret regular expressions as extended (modern) regular expressions rather than basic regu-

             lar expressions (BRE's).  The re_format(7) manual page fully describes both formats.

     -a      The files listed as parameters for the ``w'' functions are created (or truncated) before any

             processing begins, by default.  The -a option causes sed to delay opening each file until a

             command containing the related ``w'' function is applied to a line of input.

     -e command

             Append the editing commands specified by the command argument to the list of commands.

     -f command_file

             Append the editing commands found in the file command_file to the list of commands.  The edit-

             ing commands should each be listed on a separate line.

     -i extension

             Edit files in-place, saving backups with the specified extension.  If a zero-length extension

             is given, no backup will be saved.  It is not recommended to give a zero-length extension when

             in-place editing files, as you risk corruption or partial content in situations where disk

             space is exhausted, etc.

     -l      Make output line buffered.

     -n      By default, each line of input is echoed to the standard output after all of the commands have

             been applied to it.  The -n option suppresses this behavior.

     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 a ``D'' function), applies all of the commands

     with addresses that select that pattern space, copies the pattern space to the standard output, append-

     ing 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.

Sed Addresses

     An address is not required, but if specified must be a number (that counts input lines cumulatively

     across input files), a dollar (``$'') character that addresses the last line of input, or a context

     address (which 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 one address selects all of the pattern spaces that match the address.

     A command line with two addresses selects an inclusive range.  This range starts with the first pattern

     space that matches the first address.  The end of the range is the next following pattern space that

     matches the second address.  If the second address is a number less than or equal to the line number

     first selected, only that line is selected.  In the case when the second address is a context address,

     sed does not re-match the second address against the pattern space that matched the first address.

     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.

Sed Regular Expressions

     The regular expressions used in sed, by default, are basic regular expressions (BREs, see re_format(7)

     for more information), but extended (modern) regular expressions can be used instead if the -E flag is

     given.  In addition, sed has the following two additions to regular expressions:

     1.   In a context address, any character other than a backslash (``\'') or newline character may be

          used to delimit the regular expression.  Also, putting a backslash character before the delimiting

          character causes the character to be treated literally.  For example, in the context address

          \xabc\xdefx, the RE delimiter is an ``x'' and the second ``x'' stands for itself, so that the reg-

          ular expression is ``abcxdef''.

     2.   The escape sequence \n matches a newline character embedded in the pattern space.  You cannot,

          however, use a literal newline character in an 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, 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''.

Sed 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

     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 func-

     tion letter by white space.  Each file given as an argument to sed is created (or its contents trun-

     cated) before any input processing begins.

     The ``b'', ``r'', ``s'', ``t'', ``w'', ``y'', ``!'', and ``:'' functions all accept additional argu-

     ments.  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:

           { function

             function

             ...

             function

           }

     The ``{'' can be preceded by white space and can be followed by white space.  The function can be pre-

     ceded by white space.  The terminating ``}'' must be preceded by a newline or optional white space.

     [2addr] function-list

             Execute function-list only when the pattern space is selected.

     [1addr]a\

     text    Write text to standard output immediately before each attempt to read a line of input, whether

             by executing the ``N'' function or by beginning a new cycle.

     [2addr]b[label]

             Branch to the ``:'' function with the specified label.  If the label is not specified, branch

             to the end of the script.

     [2addr]c\

     text    Delete the pattern space.  With 0 or 1 address or at the end of a 2-address range, text is

             written to the standard output.

     [2addr]d

             Delete the pattern space and start the next cycle.

     [2addr]D

             Delete the initial segment of the pattern space through the first newline character and start

             the next cycle.

     [2addr]g

             Replace the contents of the pattern space with the contents of the hold space.

     [2addr]G

             Append a newline character followed by the contents of the hold space to the pattern space.

     [2addr]h

             Replace the contents of the hold space with the contents of the pattern space.

     [2addr]H

             Append a newline character followed by the contents of the pattern space to the hold space.

     [1addr]i\

     text    Write text to the standard output.

     [2addr]l

             (The letter ell.)  Write the pattern space to the standard output in a visually unambiguous

             form.  This form is as follows:

                   backslash          \\

                   alert              \a

                   form-feed          \f

                   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 ``$''.

     [2addr]n

             Write the pattern space to the standard output if the default output has not been suppressed,

             and replace the pattern space with the next line of input.

     [2addr]N

             Append the next line of input to the pattern space, using an embedded newline character to sep-

             arate the appended material from the original contents.  Note that the current line number

             changes.

     [2addr]p

             Write the pattern space to standard output.

     [2addr]P

             Write the pattern space, up to the first newline character to the standard output.

     [1addr]q

             Branch to the end of the script and quit without starting a new cycle.

     [1addr]r file

             Copy 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 con-

             dition is set.

     [2addr]s/regular expression/replacement/flags

             Substitute the replacement string for the first instance of the regular expression in the pat-

             tern space.  Any character other than backslash or newline can be used instead of a slash to

             delimit the RE and the replacement.  Within the RE and the replacement, the RE 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 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 charac-

             ter in the replacement string, precede it with a backslash.

             The value of flags in the substitute function is zero or more of the following:

                   N       Make the substitution only for the N'th occurrence of the regular expression in

                           the pattern space.

                   g       Make the substitution for all non-overlapping matches of the regular expression,

                           not just the first one.

                   p       Write 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  Append the pattern space to file 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.

     [2addr]t [label]

             Branch 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 speci-

             fied, branch to the end of the script.

     [2addr]w file

             Append the pattern space to the file.

     [2addr]x

             Swap the contents of the pattern and hold spaces.

     [2addr]y/string1/string2/

             Replace all occurrences of 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 an

             ``n'' is replaced by a newline character.  A pair of backslashes is replaced by a literal back-

             slash.  Finally, a backslash followed by any other character (except a newline) is that literal

             character.

     [2addr]!function

     [2addr]!function-list

             Apply 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]=

             Write the line number to the standard output followed by a newline character.

     [0addr]

             Empty lines are ignored.

     [0addr]#

             The ``#'' 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 sup-

             pressed.  This is the same as specifying the -n option on the command line.

ENVIRONMENT

     The COLUMNS, LANG, LC_ALL, LC_CTYPE and LC_COLLATE environment variables affect the execution of sed as

     described in environ(7).

EXIT STATUS

     The sed utility exits 0 on success, and >0 if an error occurs.

LEGACY DESCRIPTION

     Warnings are not generated for unused labels.  In legacy mode, they are.

     In the -y function, doubled backslashes are not converted to single ones.  In legacy mode, they are.

     For more information about legacy mode, see compat(5).

SEE ALSO

     awk(1), ed(1), grep(1), regex(3), compat(5), re_format(7)

STANDARDS

     The sed utility is expected to be a superset of the IEEE Std 1003.2 (``POSIX.2'') specification.

     The -E, -a and -i options are non-standard FreeBSD extensions and may not be available on other operat-

     ing systems.

HISTORY

     A sed command, written by L. E. McMahon, appeared in Version 7 AT&T UNIX.

AUTHORS

     Diomidis D. Spinellis <[email protected]>

BUGS

     Multibyte characters containing a byte with value 0x5C (ASCII `\') may be incorrectly treated as line

     continuation characters in arguments to the ``a'', ``c'' and ``i'' commands.  Multibyte characters can-

     not be used as delimiters with the ``s'' and ``y'' commands.

BSD                              May 10, 2005                              BSD