使用sed命令遇到的坑

最新推荐文章于 2024-10-19 14:47:40 发布

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最新推荐文章于 2024-10-19 14:47:40 发布

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原文链接：http://www.cnblogs.com/diveintokernel/p/9481216.html

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　　sed命令帮助

[root@unaryhost ~]# sed 
Usage: sed [OPTION]... {script-only-if-no-other-script} [input-file]...

  -n, --quiet, --silent
                 suppress automatic printing of pattern space
  -e script, --expression=script
                 add the script to the commands to be executed
  -f script-file, --file=script-file
                 add the contents of script-file to the commands to be executed
  --follow-symlinks
                 follow symlinks when processing in place; hard links
                 will still be broken.
  -i[SUFFIX], --in-place[=SUFFIX]
                 edit files in place (makes backup if extension supplied).
                 The default operation mode is to break symbolic and hard links.
                 This can be changed with --follow-symlinks and --copy.
  -c, --copy
                 use copy instead of rename when shuffling files in -i mode.
                 While this will avoid breaking links (symbolic or hard), the
                 resulting editing operation is not atomic.  This is rarely
                 the desired mode; --follow-symlinks is usually enough, and
                 it is both faster and more secure.
  -l N, --line-length=N
                 specify the desired line-wrap length for the `l' command
  --posix
                 disable all GNU extensions.
  -r, --regexp-extended
                 use extended regular expressions in the script.
  -s, --separate
                 consider files as separate rather than as a single continuous
                 long stream.
  -u, --unbuffered
                 load minimal amounts of data from the input files and flush
                 the output buffers more often
      --help     display this help and exit
      --version  output version information and exit

If no -e, --expression, -f, or --file option is given, then the first
non-option argument is taken as the sed script to interpret.  All
remaining arguments are names of input files; if no input files are
specified, then the standard input is read.

GNU sed home page: <http://www.gnu.org/software/sed/>.
General help using GNU software: <http://www.gnu.org/gethelp/>.

遇到的问题

　　在使用sed -i文件修改文件时，比如/etc/rc.local，修改成功后，重启机器，rc.local新增加的命令没有生效，手动修改rc.local可以生效。

原因是/etc/rc.local其实是一个软链接，指向的文件是/etc/rc.d/rc.local, 使用sed -i命令后，会打破原有的软链接和硬链接，修改后，/etc/rc.local不再是链接，而是普通文件，而系统实际加载的是/etc/rc.d/rc.local，所有新增加的命令没有被执行。

  -i[SUFFIX], --in-place[=SUFFIX]
                 edit files in place (makes backup if extension supplied).
                 The default operation mode is to break symbolic and hard links.
                 This can be changed with --follow-symlinks and --copy.

转载于:https://www.cnblogs.com/diveintokernel/p/9481216.html