paste

Basic Usage: Combining Files Line by Line

The simplest application of paste is combining lines from multiple files side-by-side. Let’s say we have two files, file1.txt and file2.txt:

file1.txt:

apple
banana
cherry

file2.txt:

red
yellow
red

Running the command paste file1.txt file2.txt will produce:

apple   red
banana  yellow
cherry  red

Notice the tab character separating the fields. This is the default delimiter.

Customizing the Delimiter

You can specify a different delimiter using the -d option. For example, to use a comma as the separator:

paste -d ',' file1.txt file2.txt

This will output:

apple,red
banana,yellow
cherry,red

You can also use multiple characters as a delimiter. For instance, to use ” ; ” as the delimiter:

paste -d ' ; ' file1.txt file2.txt

This outputs:

apple ; red
banana ; yellow
cherry ; red

Merging Columns Within a Single File

paste isn’t limited to combining multiple files. It can also merge columns within a single file. Consider file3.txt:

file3.txt:

one
two
three

To create a two-column output from this single file, we can use paste with the -s option (serial):

paste -s -d '|' <(echo "Column A") <(cat file3.txt)

This will output:

Column A|one
Column A|two
Column A|three

Here <() creates a process substitution. We use it to simulate two files.

Combining Multiple Files with Different Delimiters

For more complex scenarios, you can combine multiple files with different delimiters. Let’s say we have file4.txt and file5.txt:

file4.txt:

1
2
3

file5.txt:

A
B
C

We want to combine them with a comma separating file4.txt entries and a space separating the combined output:

paste -d ',' file4.txt file5.txt | paste -d ' ' - -

This first pastes file4.txt and file5.txt with a comma delimiter. Then, it pipes the result to another paste command, which treats the comma-separated output as two files (“-” represents standard input) and pastes them with a space as the delimiter. The output will be:

1,A 2,B 3,C

Handling Files with Unequal Number of Lines

When dealing with files having different numbers of lines, paste will stop at the shortest file. Lines from longer files will be truncated.

Advanced Use Cases: Combining with other Commands

paste works well in conjunction with other Linux commands. For example, you could combine paste with cut to extract specific columns and then merge them:

This section requires a more concrete example to showcase the relationship between paste and cut effectively. A specific use case with input data and desired output would provide a much clearer illustration.