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--- help:general_linux:linux_advanced [2016/05/18 13:35]
jebailie created
+++ help:general_linux:linux_advanced [2016/05/18 14:13]
jebailie
@@ Line 1: / Line 1: @@
-===== Linux Commands : advanced===
+===== Linux Commands : file - search / replace =====
+For the following cmds, the //test.file// contains:
+<code>
+cat barn food
+dog house kibble
+fish water food
+cow pasture grass
+</code>
 ==== grep ====
+"searches the named input FILE for lines containing a match to PATTERN"
+* Good for searching a file for a certain pattern
+<code>
+user@tim:~$ grep --help
+Usage: grep [OPTION]... PATTERN [FILE]...
+Search for PATTERN in each FILE or standard input.
+  // snip //
+user@tim:~$ grep cat test.file
+cat barn food
-==== diff ====
+user@tim:~$ grep food test.file
+cat barn food
+fish water food
+</code>
 ==== awk ====
+"pattern scanning and processing language"
+* good for printing columnar data, note that the field separator (between the columns) can be anything (space, tab, colon, etc)
+<code>
+user@tim:~$ cat test.file |awk '{print $2}'
+cat
+dog
+fish
+cow
+</code>
 ==== sed ====
+"stream editor for filtering and transforming text"
+<code>
+user@tim:~$ sed s/cat/lion/ test.file
+lion barn food
+dog house kibble
+fish water food
+cow pasture grass
+(note that the input file //test.file// did NOT change)
+user@tim:~$ cat test.file
+cat barn food
+dog house kibble
+fish water food
+cow pasture grass
+user@tim:~$ sed s/cat/lion/ test.file > new.file
+(save into //new.file//)
+user@tim:~$ cat new.file
+lion barn food
+dog house kibble
+fish water food
+cow pasture grass
+user@tim:~$ cat test.file
+cat barn food
+dog house kibble
+fish water food
+cow pasture grass
+</code>