basename

Updated

September 4, 2026

Overview

basename strips the directory portion (and optionally a suffix) from a path, leaving the final component. It is the complement of dirname for simple path surgery in shell scripts — naming logs, deriving output files, and parsing $0.

Syntax

basename NAME [SUFFIX]
basename OPTION... NAME...

Common Options

Option Description
-a, --multiple Treat all arguments as NAMEs
-s SUF, --suffix=SUF Strip suffix (implies multiple mode when combined properly)
-z, --zero NUL-terminated output

Traditional form: basename /path/to/file.txt .txt → file.

Key Use Cases

  1. Extract filename from a path
  2. Strip extensions
  3. Derive names from $0 or CLI args
  4. Build sibling output paths in loops
  5. Clean display names in logs

Examples with Explanations

Basics

basename /path/to/file.txt
# file.txt
basename /path/to/file.txt .txt
# file
basename /path/to/dir/
# dir
basename /
# /   (or implementation-defined root behavior)

Multiple names

basename -a /a/b /c/d
basename -a -s .conf /etc/ssh/sshd_config /etc/systemd/logind.conf

Script name

SCRIPT_NAME=$(basename "$0")
echo "usage: $SCRIPT_NAME [options]"

Strip extension patterns

f=/data/report.2024.csv
base=$(basename "$f")           # report.2024.csv
stem=$(basename "$f" .csv)      # report.2024
# careful: only strips exact suffix match at end

Loop rename

for f in /var/log/app/*.log; do
  b=$(basename "$f")
  gzip -c "$f" > "/backup/${b}.gz"
done

Combine with dirname

path=/opt/app/bin/tool
echo "dir=$(dirname "$path") name=$(basename "$path")"

NUL-safe pipeline

find . -type f -name '*.md' -print0 |
  while IFS= read -r -d '' f; do
    basename -z "$f"
  done

Parameter expansion alternative

# bash-only equivalents often used instead of basename
f=/path/to/file.txt
echo "${f##*/}"           # file.txt
echo "${f##*/}" | sed 's/\.txt$//'
# or
b=${f##*/}; echo "${b%.txt}"

Builtins avoid spawning basename in hot loops.

Notes / Pitfalls

  • Suffix strip requires an exact trailing match; .tar.gz must be stripped carefully (often twice or with special logic).
  • Trailing slashes: GNU basename handles them; still quote variables.
  • Don’t use for security canonicalization — use realpath / proper validation.
  • BusyBox basename may lack -a/-z.
  • Filenames with newlines need -z / careful reading.

2026-relevant notes

  • In hot path bash, prefer ${var##*/} over external basename.
  • Still excellent for readability in admin scripts and one-liners.
  • Pair with realpath when the path may contain .. or symlinks before basenaming for display only.

Additional Resources

  • man basename