preface
sed, whose full name is stream editor, is a stream editor for text processing and supports regular expressions. sed processes text one line at a time
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sed syntax
- Example: sed - I's / original string / new string / '/ home / test txt
- The sed command deals with the contents of the schema space rather than directly dealing with the contents of the file. If the parameter i is added, the file content is modified directly
sed [-nefr parameter] [action] [file]
| Options and parameters | describe |
|---|---|
| -n | Use silent mode. In the general sed usage, the input data will be output to the screen. However, if the - n parameter is added, it will not be displayed. If the p flag is followed, the row specially processed by sed will be listed |
| -e | Edit the sed action directly on the command line interface and execute multiple subcommands |
| -f | Write the sed action in a file, - f filename executes the sed action of the script file |
| -r | sed's actions support the syntax of extended regular expressions |
| -i | Directly modify the read file content |
- Option - n is set to quiet mode after adding the - N option, that is, the default printing information will not be output. Unless the print p option is specially specified in the subcommand, only the lines matching the modification will be printed
---- Print both lines ---- server11:~/test # echo -e 'hello \n world' | sed 's/hello/csc/' csc world ---- Not a single line was printed ----- server11:~/test # echo -e 'hello \n world' | sed -n 's/hello/csc/' ---- Matched lines printed ----- server11:~/test # echo -e 'hello \n world' | sed -n 's/hello/csc/p' csc
- Option - e, multiple subcommands operate continuously
echo -e 'hello world' | sed -e 's/hello/csc/' -e 's/world/lwl/' result: csc lwl
- Option - i, directly modify the contents of the read file
server11:~/test # cat file.txt hello world server11:~/test # sed 's/hello/lwl/' file.txt lwl world server11:~/test # cat file.txt hello world ---- Add parameters i You can modify the file content directly---- server11:~/test # sed -i 's/hello/lwl/' file.txt lwl world server11:~/test # cat file.txt hello world
- Option - f, execute file script
sed.script Script content: s/hello/A/ s/world/B/ ------ echo "hello world" | sed -f sed.script result: A B
- Option - r, support regular expressions
echo "hello world" | sed -r 's/(hello)|(world)/csc/g' csc csc
Action: [n1[,n2]] function
n1, n2: optional, generally stands for "select the number of rows to perform the action". For example, if the action needs to be performed between 10 and 20 rows, it is expressed as 10,20 [function]
test.txt content 111 222 333 444 ----- Delete all lines not between line 2 and line 3 ---------- server11:~ # sed -i '2,3!d' test.txt server11:~ # cat test.txt 222 333
function has the following options
| function | describe |
|---|---|
| a | New: a can be followed by strings, and these strings will appear on a new line (the current next line) |
| i | Insert: i can be followed by strings, and these strings will appear on a new line (the current previous line) |
| c | Substitution: c can be followed by strings, which can replace the lines between N1 and N2 |
| d | Delete: because it is deleted, there is usually nothing after d |
| p | Print: also print a selected data. Usually p runs with the parameter sed -n |
| s | Substitution: you can directly carry out the work of substitution! Usually this s action can be matched with regular expressions! For example: 1,20 s/old/new/g |
- function: - A, insert a new line after the line
sed -i '/Specific string/a New line string' fileName
- function: - i, insert a new line before the line
sed -i '/Specific string/i New line string' fileName
- function: - c, modify the specified content line
sed -i '/Specific string/c csc lwl' fileName
- function: - d, delete a specific string
sed -i '/Specific string/d' fileName
sed s subcommand: s/{pattern}/{replacement}/{flags}
-
If {pattern} contains regular expressions, you need to add - r
-
If there is a group in {pattern}, "\ n" in {replacement} represents the nth group and "&" represents the whole matching string. See the ex amp le for details
-
The parameters of flags are as follows
| flags | describe |
|---|---|
| n | It can be 1-512, indicating the replacement of the n-th occurrence |
| g | Global change |
| p | Print the contents of the mode space |
| w file | Write to a file |
- Examples
server11:~ # echo -e 'hello 1112 world' | sed -r 's/([a-z]+)( [0-9]+ )([a-z]+)/&/' hello 1112 world server11:~ # echo -e 'hello 1112 world' | sed -r 's/([a-z]+)( [0-9]+ )([a-z]+)/\3\2\1/' world 1112 hello