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title Linux Command Tutorial: cut
date 2026-09-12 00:00:00 +0000
categories
Technology
tags
Linux
GNU Coreutils
cut
Linux Command Tutorial
draft false
slug linux-cut-tutorial
description Authoritative reference tutorial for cut (GNU Coreutils), detailing column slicing by bytes (-b), characters (-c), and fields (-f), delimiter handling, and POSIX portability.
upstream_suite gnu-coreutils
upstream_version GNU Coreutils 9.11
posix_standard POSIX.1-2024
research_date 2026-09-12

The Linux Command Tutorial series provides rigorous, upstream-verified references for essential system commands across Linux distributions and UNIX-like environments. Each article focuses on a single executable, combining exhaustive option documentation, verified real-world examples, security boundaries, and best practices directly derived from official source documentation and POSIX standards.

1. Introduction

Upstream: GNU Coreutils 9.11 | POSIX: POSIX.1-2024 (with GNU extensions) | Safety Tier: safe-read-only | Scope: text-processing

cut removes sections from each line of files or standard input. It extracts column fields based on delimiters (e.g. commas, tabs, colons) or slices exact byte/character offsets.

  • Upstream Project & Provenance: Distributed in GNU Coreutils (coreutils).
  • Portability & Standards Baseline: Standardized in IEEE Std 1003.1-2024 (POSIX.1-2024). GNU cut introduces custom output delimiters (--output-delimiter), complement ranges (--complement), and zero-terminated records (-z).
  • Target Research Implementation: Audited against GNU Coreutils 9.11 (cut(1)).
  • Applicability & Lifecycle: The lightweight choice for slicing delimited files (CSV, TSV, /etc/passwd) without spawning heavy language runtimes.

2. Syntax and Command Model

2.1 Canonical Synopsis

cut OPTION... [FILE]...

2.2 Execution Model & Modes

cut requires specifying exactly one extraction mode:

  1. Bytes (-b LIST): Selects byte offsets (1-indexed).
  2. Characters (-c LIST): Selects character offsets (multi-byte safe in UTF-8).
  3. Fields (-f LIST): Selects delimited fields separated by -d.

3. Options

3.1 Primary Operational Flags

Short Flag Long Flag Description POSIX Defined
-b LIST --bytes=LIST Select only these bytes. Yes
-c LIST --characters=LIST Select only these characters. Yes
-d CHAR --delimiter=CHAR Use CHAR instead of TAB for field delimiter. Yes
-f LIST --fields=LIST Select only these fields. Yes
-s --only-delimited Do not print lines not containing delimiters. Yes
N/A --complement Complement the set of selected bytes, characters or fields. No
N/A --output-delimiter=STRING Use STRING as the output delimiter (default is input delimiter). No
-z --zero-terminated Line delimiter is NUL (\0), not newline. No

4. Basic Usage

4.1 Quick-Reference Cheatsheet Card

Operation Command Notes
Extract 1st column (colon-delimited) cut -d: -f1 /etc/passwd Slices field 1 using delimiter :
Extract multiple fields cut -d, -f1,3 data.csv Extracts 1st and 3rd fields
Extract field range cut -d$'\t' -f2-4 table.tsv Extracts fields 2 through 4 tab-delimited
Slice fixed-width characters cut -c 1-10 fixed.txt Extracts characters 1 through 10
Invert field selection cut -d, --complement -f2 data.csv Drops column 2, keeping all other fields
Change output delimiter cut -d: -f1,7 --output-delimiter=" " /etc/passwd Replaces delimiter in output stream
Suppress non-delimited lines cut -d, -f2 -s mixed.csv Ignores comment or unseparated lines

4.2 Extracting Usernames from /etc/passwd

cut -d: -f1 /etc/passwd | head -n 4
root
daemon
bin
sys

4.3 Slicing Multiple Non-Contiguous Fields

cut -d: -f1,6,7 /etc/passwd | head -n 2
root:/root:/bin/bash
daemon:/usr/sbin:/usr/sbin/nologin

5. Practical Operations

5.1 Changing Delimiters on the Fly via --output-delimiter

Transforming a colon-delimited /etc/passwd line into a space-separated format:

cut -d: -f1,3,6 --output-delimiter=" | " /etc/passwd | head -n 3
root | 0 | /root
daemon | 1 | /usr/sbin
bin | 2 | /bin

5.2 Dropping Specific Columns with --complement

Removing the middle column (Field 2) from a 3-column CSV:

echo "Alice,SecretData,Engineer" | cut -d, --complement -f2
Alice,Engineer

5.3 Slicing Fixed-Width Character Columns

Extracting fixed-width columns (characters 1–10 and 20–30):

cut -c 1-10,20-30 fixed_records.txt

6. Advanced Usage

6.1 Suppressing Non-Delimited Lines with -s

By default, lines that do not contain the delimiter are printed unmodified. In scripts processing CSV headers or mixed logs, this causes dirty lines. Passing -s suppresses non-matching lines:

cut -d, -f2 -s data_with_comments.csv
  • Lines lacking a comma are discarded.

7. Exit Status, Environment, and Configuration

7.1 Exit Status Codes

Exit Code Meaning
0 Success: fields extracted cleanly.
>0 An error occurred (multiple selection modes specified, invalid field range, file unreadable).

8. Safety, Security, and Portability

8.1 Single-Character Delimiter Limitation

Note

cut strictly accepts a single byte/character as its delimiter (-d). It cannot split streams using multi-character patterns (e.g., ::) or variable-length whitespace (\s+). For multi-character delimiters or irregular whitespace columns, use awk -F"::" or awk '{print $1}'.

9. Best Practices

  1. Use cut for Simple Delimited Slicing Over awk:
    • Guidance: For single-character delimited field extraction (cut -d: -f1), prefer cut.
    • Authoritative Justification: GNU documentation notes cut is a lightweight C binary with minimal memory footprint and faster throughput than AWK interpreters.
  2. Always Use -s on Delimited Log Files:
    • Guidance: Supply -s when processing CSV files that might contain comments or blank lines.
    • Authoritative Justification: Prevents non-delimited lines from passing through into column pipelines.
  3. Use --complement for Inverted Slices:
    • Guidance: Strip unwanted fields using --complement rather than listing all remaining fields.
    • Authoritative Justification: Reduces brittle hardcoded column indexes in scripts.

References

  1. GNU Coreutils cut Manual: https://www.gnu.org/software/coreutils/manual/html_node/cut-invocation.html
  2. POSIX.1-2024 cut Specification: The Open Group Base Specifications Issue 8. https://pubs.opengroup.org/onlinepubs/9799919799/utilities/cut.html