sed 範例四

1. 練習：取出 /etc/man.config 檔案的內容中有 MANPATH 的設定，但其中包含以 "#" 開始的註解，請再利用管線命令以 sed 刪除註解行。

   [dywang@dywmac ~]$ grep MANPATH /etc/man.config
   # when MANPATH contains an empty substring), to find out where the cat
   # MANPATH		manpath_element	[corresponding_catdir]
   # MANPATH_MAP		path_element	manpath_element
   # Every automatically generated MANPATH includes these fields
   MANPATH	/usr/man
   MANPATH	/usr/share/man
   MANPATH	/usr/local/man
   MANPATH	/usr/local/share/man
   MANPATH	/usr/X11R6/man
   # MANPATH	/opt/*/man
   # MANPATH	/usr/lib/*/man
   # MANPATH	/usr/share/*/man
   # MANPATH	/usr/kerberos/man
   # Set up PATH to MANPATH mapping
   MANPATH_MAP	/bin			/usr/share/man
   MANPATH_MAP	/sbin			/usr/share/man
   MANPATH_MAP	/usr/bin		/usr/share/man
   MANPATH_MAP	/usr/sbin		/usr/share/man
   MANPATH_MAP	/usr/local/bin		/usr/local/share/man
   MANPATH_MAP	/usr/local/sbin		/usr/local/share/man
   MANPATH_MAP	/usr/X11R6/bin		/usr/X11R6/man
   MANPATH_MAP	/usr/bin/X11		/usr/X11R6/man
   MANPATH_MAP	/usr/bin/mh		/usr/share/man
   

2. 取出 /etc/man.config 檔案的內容中有 MANPATH 的設定解答。 且刪除註解說明。

   [dywang@dywmac ~]$ grep MANPATH /etc/man.config | sed '/^#/d'
   MANPATH	/usr/man
   MANPATH	/usr/share/man
   MANPATH	/usr/local/man
   MANPATH	/usr/local/share/man
   MANPATH	/usr/X11R6/man
   MANPATH_MAP	/bin			/usr/share/man
   MANPATH_MAP	/sbin			/usr/share/man
   MANPATH_MAP	/usr/bin		/usr/share/man
   MANPATH_MAP	/usr/sbin		/usr/share/man
   MANPATH_MAP	/usr/local/bin		/usr/local/share/man
   MANPATH_MAP	/usr/local/sbin		/usr/local/share/man
   MANPATH_MAP	/usr/X11R6/bin		/usr/X11R6/man
   MANPATH_MAP	/usr/bin/X11		/usr/X11R6/man
   MANPATH_MAP	/usr/bin/mh		/usr/share/man
   

3. sed 加參數 -e 同時完成刪除與取代命令。例如： grep -v 取出 /etc/man.config 不是註解的設定行，再利用 sed 刪除檔案第 10 行至最後一行，且將字串 MAN 改成 man。

   [dywang@dywmac ~]$ grep -v '^#' /etc/man.config | sed -e '10,$d' -e 's/MAN/man/g'
   FHS
   manPATH	/usr/man
   manPATH	/usr/share/man
   manPATH	/usr/local/man
   manPATH	/usr/local/share/man
   manPATH	/usr/X11R6/man
   manPATH_MAP	/bin			/usr/share/man
   manPATH_MAP	/sbin			/usr/share/man
   manPATH_MAP	/usr/bin		/usr/share/man
   

4. 如果 sed 要同時執行很多動作，可以將這些動作寫在一個檔案中，再以 -f 選項指令檔案執行 sed 命令。例如將上例刪除與取代命令編輯至檔案 ds.src，執行結果一樣。

   [dywang@dywmac zzz]$ vim ds.src
   [dywang@dywmac zzz]$ cat ds.src
   10,$d
   s/MAN/man/g
   
   [dywang@dywmac zzz]$ grep -v '^#' /etc/man.config | sed -f ds.src 
   FHS
   manPATH	/usr/man
   manPATH	/usr/share/man
   manPATH	/usr/local/man
   manPATH	/usr/local/share/man
   manPATH	/usr/X11R6/man
   manPATH_MAP	/bin			/usr/share/man
   manPATH_MAP	/sbin			/usr/share/man
   manPATH_MAP	/usr/bin		/usr/share/man