How to use the command 'cut' (with examples)

The cut command is a powerful utility in Unix and Unix-like operating systems used for cutting out sections from each line of files or standard input. It is a versatile tool that allows users to select specific portions of text, either by character, byte, or field. This capability is particularly useful in scenarios where data parsing and manipulation are required, such as processing log files, extracting data from CSV files, or formatting output for custom reports.

Use case 1: Print a specific character/field range of each line

Code:

command | cut --characters 1-10

Motivation:

This example is particularly beneficial when dealing with structured data or text where only a specific portion of each line is relevant. For instance, in a scenario where you’re processing log files, and you only need the first ten characters of each line, perhaps because they contain a date or unique identifier, using cut allows for efficient extraction without having to manually sift through potentially large datasets.

Explanation:

• command: Represents the command whose output you want to process. This could be any utility or script that provides input data to cut.
• |: The pipe operator channels the output of one command as input to another.
• cut: The command used to extract sections from lines of text.
• --characters 1-10: Specifies that you want the first ten characters from each line. The 1-10 denotes a range starting from character 1 to character 10.

Example output:

2023-01-A
2023-01-B
2023-01-C

Here, each line begins with a date followed by a unique identifier, and only the first ten characters, representing the date, are extracted.

Use case 2: Print a field range of each line with a specific delimiter

Code:

command | cut --delimiter "," --fields 1

Motivation:

This use case is invaluable when working with CSV (Comma-Separated Values) data files. Imagine you are tasked with extracting the first column, which perhaps holds the names of individuals, from a CSV file containing multiple columns of data. Using cut makes it easy to isolate and retrieve the desired data field based on the specified delimiter.

Explanation:

• command: The initial command that produces data to be filtered. This could be a cat command, a script execution, or the output of another command.
• |: The pipe operator facilitates the transfer of data between commands.
• cut: The main command used to selectively extract content.
• --delimiter ",": Indicates that the fields are separated by commas, common in CSV files.
• --fields 1: Specifies the extraction of the first field from each line, leveraging the delimiter to identify field boundaries.

Example output:

John
Jane
Bob

In this result, each name extracted is the first field in a CSV containing people’s details.

Use case 3: Print a character range of each line of the specific file

Code:

cut --characters 1 path/to/file

Motivation:

This command is useful when you need to view or extract specific characters from each line within a text file. For example, if each line in your file starts with a status indicator, and you’re interested in extracting just that specific indicator, utilizing the cut command can quickly display those characters.

Explanation:

• cut: The tool used for line-by-line text extraction.
• --characters 1: Targets the extraction of only the first character from each line.
• path/to/file: The path to the file you want to process, specifying the source of the textual data.

Example output:

A
B
C

Assuming each line in the file starts with a single-character status, this output shows that the first character from each line is successfully extracted.

Use case 4: Print specific fields of NUL terminated lines

Code:

command | cut --zero-terminated --fields 1

Motivation:

This command has particular relevance in contexts where filenames or data entries contain spaces or newline characters. For instance, when using the find command with -print0 option to handle filenames that contain spaces, using cut with zero termination ensures that the extraction process remains robust and accurately processes each entry as a single line.

Explanation:

• command: Represents the root command providing input, often a find command with -print0.
• |: Pipe operator connecting the input of one application to another.
• cut: The utility for extracting specified data.
• --zero-terminated: Specifies that the lines are terminated by a NUL character (\0) instead of a newline, matching the output of find . -print0.
• --fields 1: Extracts only the first field of the NUL-separated list.

Example output:

file1.txt
file2.txt
file3.txt

This reflects the filename of each file found, properly extracted even if filenames include spaces.

Conclusion:

These diverse examples demonstrate the versatility of the cut command in handling and manipulating text data efficiently. Whether working with CSV files, complex logs, or filenames containing special characters, cut provides a simple yet powerful mechanism to filter and extract necessary information from large datasets, enhancing data processing workflows. Understanding the wide range of options available with the cut command can significantly streamline and improve text manipulation tasks in Unix-based environments.