Paste Command in Linux (Merge Lines)

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paste is a command that allows you to merge lines of files horizontally. It outputs lines consisting of the sequentially corresponding lines of each file specified as an argument, separated by tabs.

In this tutorial, we will explain how to use the paste command.

How to Use the paste Command

paste is one of the lesser-known and used Linux and Unix command-line utilities.

The general syntax for the paste command is as follows:

paste [OPTION].. [FILE]...

If no input files are provided or when - is given as argument, paste uses the standard input.

Suppose we have the following files:

file1
Iron Man
Thor
Captain America
Hulk
Spider Man
file2
Black Widow
Captain Marvel
Dark Phoenix
Nebula

When invoked without an option paste will read all files given as arguments and horizontally merge the corresponding lines of the files, separated by space:

paste file1 file2
Iron Man	Black Widow
Thor	Captain Marvel
Captain America	Dark Phoenix
Hulk	Nebula
Spider Man

Instead of displaying the output to the screen, you can redirect it to a file using the >, >> operators:

paste file1 file2 > file3

If the file doesn't exist, it will be created. The > operator will overwrite an existing file, while the >> operator will append the output to the file.

The -d, -delimiters option allows you to specify a list of characters to be used as delimiters instead of the the default TAB separator.

Each delimiter is consecutively used. When the list is exhausted, paste starts again from the first delimiter character.

To use the _ (underscore) character as a delimiter instead of TAB, you would type:

paste -d '_' file1 file2
Iron Man_Black Widow
Thor_Captain Marvel
Captain America_Dark Phoenix
Hulk_Nebula
Spider Man_

Here is an example of using two delimiters:

paste -d '%|' file1 file2 file1

The lines from the first and the second file are separated with the first character from the delimiters list. The second and the third file lines are separated with the second delimiter.

If more files were given, paste starts again from the beginning of the list.

Iron Man%Black Widow|Iron Man
Thor%Captain Marvel|Thor
Captain America%Dark Phoenix|Captain America
Hulk%Nebula|Hulk
Spider Man%|Spider Man  

The -s, --serial option tells paste to display the lines of one file at a time instead of one line from each file.

paste -s file1 file2

The command will merge all lines from the given file in separated lines:

Iron Man	Thor	Captain America	Hulk	Spider Man
Black Widow	Captain Marvel	Dark Phoenix	Nebula

When used with the -z, --zero-terminated option, paste uses a null character to delimit the items instead of the default newline character. This behavior is handy when paste is used in combination with find -print0 and xargs -0 commands to handle file names containing special characters.

Conclusion

The paste command is used to merge corresponding lines of given files.

If you have any questions or feedback, feel free to leave a comment.