{"id":2374,"date":"2016-12-20T17:15:17","date_gmt":"2016-12-20T15:15:17","guid":{"rendered":"http:\/\/www.systemcodegeeks.com\/?p=2374"},"modified":"2017-12-13T15:56:13","modified_gmt":"2017-12-13T13:56:13","slug":"sed-stream-editor-example","status":"publish","type":"post","link":"https:\/\/www.systemcodegeeks.com\/shell-scripting\/bash\/sed-stream-editor-example\/","title":{"rendered":"A Sed (Stream Editor) Example"},"content":{"rendered":"

This is a Sed (Stream Editor) example. A Stream Editor is used to perform basic transformations on text read from a file or a pipe. The result is sent to standard output. The syntax for the sed command has no output file specification, but results can be saved to a file using output redirection. The editor does not modify the original input.
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\nWhat distinguishes sed from other editors, such as vi and ed, is its ability to filter text that it gets from a pipeline feed. You do not need to interact with the editor while it is running; that is why sed is sometimes called a batch editor. This feature allows use of editing commands in scripts, greatly easing repetitive editing tasks. When facing replacement of text in a large number of files, sed is a great help.<\/p>\n

The following table shows an overview of the whole article:<\/p>\n

\n

Table Of Contents<\/h3>\n
\n
1. SED Commands<\/a><\/dt>\n
\n
\n
1.1 SED editing commands<\/a><\/dt>\n<\/dl>\n<\/dd>\n
\n
\n
1.2 Sed options<\/a><\/dt>\n<\/dl>\n<\/dd>\n
2. Interactive editing<\/a><\/dt>\n
\n
\n
2.1 Printing lines containing a pattern<\/a><\/dt>\n<\/dl>\n<\/dd>\n
\n
\n
2.2 Deleting lines of input containing a pattern<\/a><\/dt>\n<\/dl>\n<\/dd>\n
\n
\n
2.3 Ranges of lines<\/a><\/dt>\n<\/dl>\n<\/dd>\n
\n
\n
2.4 Find and replace with sed<\/a><\/dt>\n<\/dl>\n<\/dd>\n
3. Non-interactive editing<\/a><\/dt>\n
\n
\n
3.1 Reading sed commands from a file<\/a><\/dt>\n<\/dl>\n<\/dd>\n
\n
\n
3.2 Writing output files<\/a><\/dt>\n<\/dl>\n<\/dd>\n
4. Summary<\/a><\/dt>\n<\/dl>\n<\/div>\n

<\/a>1. SED Commands<\/h2>\n

The sed program can perform text pattern substitutions and deletions using regular expressions, like the ones used with the grep command. The editing commands are similar to the ones used in the vi editor.<\/p>\n

<\/a>1.1 SED editing commands<\/h3>\n\n\n\n\n\n\n\n\n\n\n\n
Command<\/th>\nResult<\/th>\n<\/tr>\n
a\\<\/td>\nAppend text below current line.<\/td>\n<\/tr>\n
c\\<\/td>\nChange text in the current line with new text.<\/td>\n<\/tr>\n
d<\/td>\nDelete text.<\/td>\n<\/tr>\n
i\\<\/td>\nInsert text above current line.<\/td>\n<\/tr>\n
p<\/td>\nPrint text.<\/td>\n<\/tr>\n
r<\/td>\nRead a file.<\/td>\n<\/tr>\n
s<\/td>\nSearch and replace text.<\/td>\n<\/tr>\n
w<\/td>\nWrite to a file.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

<\/a>1.2 Sed options<\/h3>\n\n\n\n\n\n\n\n
Option<\/th>\nEffect<\/th>\n<\/tr>\n
-e SCRIPT<\/td>\nAdd the commands in SCRIPT to the set of commands to be run while processing the input.<\/td>\n<\/tr>\n
-f<\/td>\nAdd the commands contained in the file SCRIPT-FILE to the set of commands to be run while processing the input.<\/td>\n<\/tr>\n
-n<\/td>\nSilent mode.<\/td>\n<\/tr>\n
-V<\/td>\nPrint version information and exit.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

<\/a>2. Interactive editing<\/h2>\n

<\/a>2.1 Printing lines containing a pattern<\/h3>\n

This is something you can do with grep, of course, but you can’t do a “find and replace” using that command. This is just to get you started.<\/p>\n

This is our example text file:<\/p>\n

Test.txt<\/em><\/span><\/p>\n

We shall not spend a large expense of time\r\nBefore we reckon with your several loves,\r\nAnd make us even with you. My thanes and kinsmen,\r\nHenceforth be earls, the first that ever Scotland\r\nIn such an honour named. What's more to do,\r\nWhich would be planted newly with the time,\r\nAs calling home our exiled friends abroad\r\nThat fled the snares of watchful tyranny;\r\nProducing forth the cruel ministers\r\nOf this dead butcher and his fiend-like queen,\r\nWho, as 'tis thought, by self and violent hands\r\nTook off her life; this, and what needful else\r\nThat calls upon us, by the grace of Grace,\r\nWe will perform in measure, time and place:\r\nSo, thanks to all at once and to each one,\r\nWhom we invite to see us crown'd at Scone.\r\nMacbeth, William Shakespeare\r\n<\/pre>\n
We want sed to find all the lines containing our search pattern, in this case “erors”. We use the p to obtain the result:<\/p>\n
\"A<\/a>
A SED Search Pattern Example.<\/figcaption><\/figure>\n
As you notice, sed prints the entire file, but the lines containing the search string are printed twice. This is not what we want. In order to only print those lines matching our pattern, use the -n option:<\/p>\n
\"A<\/a>
A SED Search Pattern Example without duplicates.<\/figcaption><\/figure>\n
<\/a>2.2 Deleting lines of input containing a pattern<\/h3>\n
We use the same example text file. Now we only want to see the lines not containing the search string:<\/p>\n
\"A<\/a>
A SED Search Pattern Example without lines containing “you”.<\/figcaption><\/figure>\n
The d command results in excluding lines from being displayed. Matching lines starting with a given pattern and ending in a second pattern are showed like this:<\/p>\n
\"A<\/a>
A SED Search Pattern Example with a given pattern and ending in a second pattern.<\/figcaption><\/figure>\n
Note that the last dot needs to be escaped in order to actually match. In our example the expression just matches any character, including the last dot.<\/p>\n
<\/a>2.3 Ranges of lines<\/h3>\n
This time we want to take out the lines containing the errors. In the example these are lines 2 to 4. Specify this range to address, together with the d command:<\/p>\n
\"A<\/a>
A SED range of line Example.<\/figcaption><\/figure>\n
To print the file starting from a certain line until the end of the file, use a command similar to this:<\/p>\n
\"Another<\/a>
Another SED range of line Example.<\/figcaption><\/figure>\n
This only prints the first two lines of the example file. The following command prints the first line containing the pattern “a text”, up to and including the next line
\ncontaining the pattern “a line”:<\/p>\n
\"A<\/a>
A SED range of line Example with two patterns.<\/figcaption><\/figure>\n
<\/a>2.4 Find and replace with sed<\/h3>\n
In the example file, we will now search and replace the errors instead of only (de)selecting the lines containing the search string.<\/p>\n
\"A<\/a>
A simple SED Find and Replace Example.<\/figcaption><\/figure>\n
To insert a string at the beginning of each line of a file, for instance for quoting:<\/p>\n
\"A<\/a>
A SED String insertion Example.<\/figcaption><\/figure>\n
Insert some string at the end of each line:<\/p>\n
\"Another<\/a>
Another SED String insertion Example.<\/figcaption><\/figure>\n
Multiple find and replace commands are separated with individual -e options:<\/p>\n
\"A<\/a>
A Sed Example with multiple find and replace commands.<\/figcaption><\/figure>\n
Keep in mind that by default sed prints its results to the standard output, most likely your terminal window. If
\nyou want to save the output to a file, redirect it:<\/p>\n
sed option 'some\/expression' file_to_process > sed_output_in_a_file\r\n<\/pre>\n
<\/a>3. Non-interactive editing<\/h2>\n
<\/a>3.1 Reading sed commands from a file<\/h3>\n
Multiple sed commands can be put in a file and executed using the -f option. When creating such a file,
\nmake sure that:<\/p>\n