REALPATH(1) General Commands Manual REALPATH(1)

realpath — resolve a pathname

realpath [-E | -e] file

The realpath utility shall canonicalize the pathname specified by the file operand as follows:

If a call to the realpath(3) function with the specified pathname as its first argument would succeed, the canonicalized pathname shall be the pathname that would be returned by that realpath(3) call. Otherwise:

  • If the -e option is specified, the canonicalization shall fail.
  • If the -E option is specified, then if a call to the realpath(3) function with the specified pathname as its first argument would encounter an error condition other than [ENOENT], the canonicalization shall fail; if the call would encounter an [ENOENT] error, realpath shall expand all symbolic links that would be encountered in an attempt to resolve the specified pathname using the algorithm specified in XBD V1_chap04(7), except that any trailing <slash> characters that are not also leading <slash> characters shall be ignored. If this expansion succeeds and the path prefix of the expanded pathname resolves to an existing directory, the canonicalized pathname shall be the expanded pathname. In all other cases, the canonicalization shall fail. If the expanded pathname is not empty, does not begin with a <slash>, and has exactly one pathname component, it shall be treated as if it had a path prefix of "./".
  • If no options are specified, realpath shall canonicalize the specified pathname in an unspecified manner such that the resulting absolute pathname does not contain any components that refer to files of type symbolic link and does not contain any components that are dot or dot-dot.

Upon successful canonicalization, realpath shall write the canonicalized pathname, followed by a <newline> character, to standard output.

If canonicalization fails, or the canonicalized pathname is empty, nothing shall be written to standard output, a diagnostic message shall be written to standard error, and realpath shall exit with non-zero status.

The realpath utility shall conform to XBD V1_chap12(7).

The following options shall be supported:

Do not treat it as an error if attempting to resolve the last component of the canonicalized form of the file operand results in an [ENOENT] error condition.
Treat it as an error if attempting to resolve the last component of the canonicalized form of the file operand results in an [ENOENT] error condition.

Specifying more than one of the mutually-exclusive options -E and -e shall not be considered an error. The last option specified shall determine the behavior of the utility.

The following operand shall be supported:

file
A pathname to be canonicalized.

Not used.

None.

The following environment variables shall affect the execution of realpath:

Provide a default value for the internationalization variables that are unset or null. (See XBD for the precedence of internationalization variables used to determine the values of locale categories.)
If set to a non-empty string value, override the values of all the other internationalization variables.
Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments and input files).

Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
[ XSI] Determine the location of messages objects and message catalogs.

Default.

See DESCRIPTION.

The standard error shall be used only for diagnostic messages.

None.

None.

The following exit values shall be returned:

Successful completion.
An error occurred.

Default.

If neither the -e nor the -E option is specified, some implementations behave as if -e had been specified and others as if -E had been specified, but there are also implementations where the behavior differs from both of these. For example, the shell has an internal implementation of realpath that canonicalizes to , whereas the realpath(3) function would return an [ENOTDIR] error in this case. Portable applications should always specify either -e or -E.

None.

The realpath utility was added in preference to a -f option found in some implementations of the readlink(1) utility because it allows the application to specify whether or not a missing final component is to be treated as an error.

The behavior with the -E option when file does not resolve (with symbolic links followed) to an existing file is not the same as simply calling realpath(3) with the path prefix of the file operand and writing the resulting pathname, a <slash>, and the last component of file to standard output. For example, if /tmp/nofile does not exist, and file is where is an existing directory and B is a symbolic link to /tmp/nofile, realpath with -E will output /tmp/nofile, but if B is a symbolic link to , realpath with -E will treat this as an error. In both cases realpath("A/B") would fail with set to [ENOENT]. Even though realpath("A") would succeed, in neither case is anything ending the result.

Trailing <slash> characters (that follow a non-<slash>) are handled differently with -E than with -e. With -e they are handled as for the realpath(3) function. With -E they are sometimes effectively ignored, and they are never included in the output. For example, if /tmp/nofile does not exist and is an existing regular file:

$ realpath -E /tmp/nofile/
/tmp/nofile
$ realpath -E /tmp/regfile/
realpath: /tmp/regfile/: Not a directory

If this utility is directed to display a pathname that contains any bytes that have the encoded value of a <newline> character when <newline> is a terminator or separator in the output format being used, implementations are encouraged to treat this as an error. A future version of this standard may require implementations to treat this as an error.

ln(1), ls(1), pwd(1), readlink(1)

XBD V1_chap08(7), V1_chap12(7)

XSH V2_chap02(3), realpath(3)

First released in Issue 8.

June 14, 2024 posix.fail