Linux Command paste and 3 Options

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The Linux command paste is a useful tool that allows you to merge the contents of multiple files side by side. It is primarily used to align data between files, and is frequently employed in shell scripts or data processing. In this post, we will cover the basic usage of the paste command, its options, and practical applications in detail.

What is the Linux Command paste?

The paste command is used to merge lines from multiple files into a single line. It combines each line from the files side by side, separating them by spaces or tabs. This tool can be applied to anything from simple data merging to more complex data manipulation tasks.

Basic Usage of the paste Command

Basic Structure

paste [options] file1 file2 ...
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In this command, file1 and file2 refer to the files you want to merge. By default, the paste command merges the first line of each file side by side, and continues to merge subsequent lines in the same way. Each line is separated by a tab (\t) character.

Example: Merging with Tabs

Suppose you have the following two files, file1.txt and file2.txt:

다음과 같이 file1.txt와 file2.txt가 있다고 하겠습니다.

apple,35
banana,21
cherry,82
file1.txt
red,38
yellow,43
purple,11
file2.txt

Using the paste command, you can merge these files with a tab separator:

paste file1.txt file2.txt
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This command will merge the lines from file1.txt and file2.txt side by side, separating them by a tab, resulting in the following output:

Figure 1. Linux command paste: merging two files with tab delimiters
Figure 1. Linux command paste: merging two files with tab delimiters

Key Options

The paste command offers several options to customize how the files are merged depending on your needs.

-d, –delimiters

This option allows you to specify a delimiter other than the default tab. For example, if you want to merge the files with commas instead of tabs, you can use the -d option:

paste -d "," file1.txt file2.txt
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This command will output the merged lines with commas as delimiters, as shown below:

Figure 2. Linux command paste: using the -d option to specify delimiters
Figure 2. Linux command paste: using the -d option to specify delimiters

-s, –serial

The -s option allows you to merge all content from each file into a single line. That is, all lines from each file are concatenated into one line.

paste -s file1.txt file2.txt
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The result is that the contents of file1.txt are merged into one line, followed by the contents of file2.txt, all on separate lines:

Figure 3. Linux command paste: using the -s option to merge each file into a single line
Figure 3. Linux command paste: using the -s option to merge each file into a single line

-z, –zero-terminated

By default, the paste command separates lines with a newline character (\n). However, using the -z option, you can separate lines with a null character (\0), which can be useful in specific situations where file delimiters need to be more explicit.

Practical Applications

The paste command is not limited to simply merging files. It can also be used in more complex scripts for data analysis and manipulation.

Merging CSV Files

When you need to merge several CSV files into one, the paste command is very helpful. For instance, if each CSV file contains data from a specific column, you can merge them into a single CSV file:

paste -d "," file1.csv file2.csv > merged.csv
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Figure 4. Linux command paste: merging CSV files
Figure 4. Linux command paste: merging CSV files

Merging Specific Columns

By combining the paste command with the cut command, you can merge only specific columns from the files. For example, to merge just the first column from two files, you can do the following:

paste <(cut -f1 -d, file1.txt) <(cut -f1 -d, file2.txt)
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This command will extract the first column from both file1.txt and file2.txt and merge them side by side.

Figure 5. Linux command paste: Combining specific columns using the cut command
Figure 5. Linux command paste: Combining specific columns using the cut command

Things to Watch Out For

There are a few important considerations when using the paste command:

  • Uneven Line Counts: If the files being merged have different numbers of lines, the paste command will leave the remaining lines from the longer file as they are. This may cause data misalignment, so it’s a good idea to check the line count of the files before merging.
  • Repeating Delimiters: If multiple delimiters are used, they will be applied in the order specified, and repeated if necessary. Be cautious, as this might not always produce the desired result.
  • Empty Files: If one of the files being merged is empty, paste will leave empty spaces for that file’s position in the output. This can lead to unintended formatting issues, so be aware of empty files.

Summary

The Linux command paste is a highly useful tool for merging file data side by side. From basic usage to more advanced options, such as changing delimiters or merging files line by line, it offers flexibility in handling data. Whether you’re merging CSV files or processing text files, paste plays an important role in scripting and data manipulation. By understanding the key options and taking note of potential pitfalls, you can efficiently handle file merging tasks using the paste command. Make use of the paste command to simplify your data processing workflow!

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