Paths command in Linux: basename, dirname, realpath, examples

Q: A path with spaces "fell apart"

Always quote it: dirname "$path". Without quotes, a space splits the arguments.

Q: realpath: No such file or directory

By default, realpath requires the path to exist. For a path that doesn't exist yet, use -m (compute it as a plain string) or -e (the opposite — require every component to exist).

Q: You need the path without resolving symlinks

realpath follows symlinks. To leave it as-is, use realpath -s (or readlink for the link itself, see ln).

Overview

Utilities for treating paths as strings — indispensable in scripts:

basename — a file's name without its directory (and, optionally, without an extension).
dirname — the directory without the file name.
realpath — the absolute path after resolving ., .. and symlinks.

bash

basename /var/log/syslog          # syslog
basename /var/log/app.log .log    # app           (strip the suffix)
dirname  /var/log/syslog          # /var/log
realpath ../../etc/nginx          # /etc/nginx    (absolute, no ../)
realpath -m /nope/x               # compute the path even if it doesn't exist (-m)

Options

6

/

Each of the three utilities has its own small set of options. basename -s strips a suffix without a separate sed call, -a takes several paths at once. realpath -e requires the whole path to actually exist, while -m does the opposite — it computes the path as a plain string even if the file doesn't exist yet; confusing the two is a common source of bugs in scripts that prepare a path for a file they're about to create themselves.

Option	What it does	Example
`-m` `--canonicalize-missing`	realpath: compute the path even if it, or part of it, does not exist.	`realpath -m /nope/x`
`-s` `--suffix` SUFFIX	basename: strip the given suffix from the name.	`basename -s .txt /a/b/c.txt`
`-e` `--canonicalize-existing`	realpath: require the whole path to exist; otherwise fail.	`realpath -e /etc/hosts`
`-s` `--strip`	realpath: do not resolve symlinks, only . and ...	`realpath -s ../x`
`-a` `--multiple`	basename: multiple names at once, each on its own line.	`basename -a /a/x /b/y`
`-z` `--zero`	Separate output entries with a NUL byte instead of a newline.	`basename -z /a/b/c.txt`

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Recipes

1

In scripts

The classic case is finding the script's own directory, so paths don't depend on where it was run from:

bash

SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"     # portable
# or shorter, with realpath:
SCRIPT_DIR="$(dirname "$(realpath "$0")")"

Splitting a path into parts:

bash

path=/srv/www/site/index.html
dir=$(dirname  "$path")           # /srv/www/site
base=$(basename "$path")          # index.html
name=$(basename "$path" .html)    # index

Plain bash gives you the same thing with parameter expansion: ${path##*/} (basename) and ${path%/*} (dirname) — no external program needed. See bash-scripting.

Troubleshooting

3

A path with spaces "fell apart"

Always quote it: dirname "$path". Without quotes, a space splits the arguments.

`realpath: No such file or directory`

By default, realpath requires the path to exist. For a path that doesn't exist yet, use -m (compute it as a plain string) or -e (the opposite — require every component to exist).

You need the path without resolving symlinks

realpath follows symlinks. To leave it as-is, use realpath -s (or readlink for the link itself, see ln).

Terms

2

absolute path: A path that starts with / and locates a file from the filesystem root; its meaning does not depend on the current directory. Example: /etc/ssh/sshd_config. Also appears in: at, Cron, ln
relative path: A path without a leading / that is resolved from the process's current directory. The components . and .. refer to the directory itself and its parent. Also appears in: systemd timers, ln, ls, tar

Paths — basename, dirname, realpath

Cheat sheet

Overview

Options

Recipes

In scripts

Troubleshooting

A path with spaces "fell apart"

`realpath: No such file or directory`

You need the path without resolving symlinks

Terms

See also