sed是Stream editor的簡稱，和vi不同，sed是行編輯器。sed特點：非互動式修改文本。

sed工作原理

sed是從檔案或管道中讀取一行，處理一行，輸出一行；再讀取一行，再處理一行，再輸出一行，直到最後一行。每當處理一行時，把目前處理的行存儲在臨時緩沖區中，這稱之為模式空間，接着用sed指令處理緩沖區中的内容，處理完成後，把緩沖區的内容送往螢幕。接着處理下一行，這樣不斷重複，直到檔案末尾。

一次處理一行的設計模式使得sed性能很高，sed在讀取大檔案時不會出現卡頓現象。如果使用vi指令打開幾十M上百M的檔案，明顯會出現有卡頓的現象，這是因為vi指令打開檔案時一次性将檔案加載到記憶體，然後再打開。sed就避免了這種情況，一行一行的處理，打開速度非常快，執行速度也很快。

[[email protected] scripts]# sed --help
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
  -i[SUFFIX], --in-place[=SUFFIX]
                 edit files in place (makes backup if SUFFIX supplied)
  -c, --copy
                 use copy instead of rename when shuffling files in -i mode
  -b, --binary
                 does nothing; for compatibility with WIN32/CYGWIN/MSDOS/EMX (
                 open files in binary mode (CR+LFs are not treated specially))
  -l N, --line-length=N
                 specify the desired line-wrap length for the `l' command
  --posix
                 disable all GNU extensions.
  -E, -r, --regexp-extended
                 use extended regular expressions in the script
                 (for portability use POSIX -E).
  -s, --separate
                 consider files as separate rather than as a single,
                 continuous long stream.
      --sandbox
                 operate in sandbox mode (disable e/r/w commands).
  -u, --unbuffered
                 load minimal amounts of data from the input files and flush
                 the output buffers more often
  -z, --null-data
                 separate lines by NUL characters
  --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: <https://www.gnu.org/software/sed/>.
General help using GNU software: <https://www.gnu.org/gethelp/>.
E-mail bug reports to: <[email protected]>.

sed基本用法

sed [option]... 'script;script;...' [inputfile]

sed常用選項

-n  不輸出模式空間内容到螢幕，即不自動列印 -n, --quiet, suppress automatic printing of pattern space
-e  多點編輯

sed輸入啥列印啥