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.TH REALPATH "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH PROLOG

This manual page is part of the POSIX Programmer's Manual.

The Linux implementation of this interface may differ (consult

the corresponding Linux manual page for details of Linux behavior),

or the interface may not be implemented on Linux.

.SH NAME

realpath

\(em resolve a pathname

.SH SYNOPSIS

.LP

.nf

#include <stdlib.h>

.P

char *realpath(const char *restrict \fIfile_name\fP,

    char *restrict \fIresolved_name\fP);

.fi

.SH DESCRIPTION

The

\fIrealpath\fR()

function shall derive, from the pathname pointed to by

.IR file_name ,

an absolute pathname that resolves to the same directory entry, whose

resolution does not involve

.BR '.' ,

.BR '..' ,

or symbolic links. If

.IR resolved_name

is a null pointer, the generated pathname shall be stored as a

null-terminated string in a buffer allocated as if by a call to

\fImalloc\fR().

Otherwise, if

{PATH_MAX}

is defined as a constant in the

.IR <limits.h> 

header, then the generated pathname shall be stored as a null-terminated

string, up to a maximum of

{PATH_MAX}

bytes, in the buffer pointed to by

.IR resolved_name .

.P

If

.IR resolved_name

is not a null pointer and

{PATH_MAX}

is not defined as a constant in the

.IR <limits.h> 

header, the behavior is undefined.

.SH "RETURN VALUE"

Upon successful completion,

\fIrealpath\fR()

shall return a pointer to the buffer containing the resolved name.

Otherwise,

\fIrealpath\fR()

shall return a null pointer and set

.IR errno

to indicate the error.

.P

If the

.IR resolved_name

argument is a null pointer, the pointer returned by

\fIrealpath\fR()

can be passed to

\fIfree\fR().

.P

If the

.IR resolved_name

argument is not a null pointer and the

\fIrealpath\fR()

function fails, the contents of the buffer pointed to by

.IR resolved_name

are undefined.

.SH ERRORS

The

\fIrealpath\fR()

function shall fail if:

.TP

.BR EACCES

Search permission was denied for a component of the path prefix of

.IR file_name .

.TP

.BR EINVAL

The

.IR file_name

argument is a null pointer.

.TP

.BR EIO

An error occurred while reading from the file system.

.TP

.BR ELOOP

A loop exists in symbolic links encountered during resolution of the

.IR file_name

argument.

.TP

.BR ENAMETOOLONG

.br

The length of a component of a pathname is longer than

{NAME_MAX}.

.TP

.BR ENOENT

A component of

.IR file_name

does not name an existing file or

.IR file_name

points to an empty string.

.TP

.BR ENOTDIR

A component of the path prefix names an existing file that is neither

a directory nor a symbolic link to a directory, or the

.IR file_name

argument contains at least one non-\c

<slash>

character and ends with one or more trailing

<slash>

characters and the last pathname component names an existing file that

is neither a directory nor a symbolic link to a directory.

.br

.P

The

\fIrealpath\fR()

function may fail if:

.TP

.BR EACCES

The

.IR file_name

argument does not begin with a

<slash>

and none of the symbolic links (if any) processed during pathname

resolution of

.IR file_name

had contents that began with a

<slash>,

and either search permission was denied for the current directory or

read or search permission was denied for a directory above the current

directory in the file hierarchy.

.TP

.BR ELOOP

More than

{SYMLOOP_MAX}

symbolic links were encountered during resolution of the

.IR file_name

argument.

.TP

.BR ENAMETOOLONG

.br

The length of a pathname exceeds

{PATH_MAX},

or pathname resolution of a symbolic link produced an intermediate

result with a length that exceeds

{PATH_MAX}.

.TP

.BR ENOMEM

Insufficient storage space is available.

.LP

.IR "The following sections are informative."

.SH EXAMPLES

.SS "Generating an Absolute Pathname"

.P

The following example generates an absolute pathname for the file

identified by the

.IR symlinkpath

argument. The generated pathname is stored in the buffer pointed to by

.IR actualpath .

.sp

.RS 4

.nf

\fB

#include <stdlib.h>

\&...

char *symlinkpath = "/tmp/symlink/file";

char *actualpath;

.P

actualpath = realpath(symlinkpath, NULL);

if (actualpath != NULL)

{

    ... use actualpath ...

.P

    free(actualpath);

}

else

{

    ... handle error ...

}

.fi \fR

.P

.RE

.SH "APPLICATION USAGE"

For functions that allocate memory as if by

\fImalloc\fR(),

the application should release such memory when it is no longer

required by a call to

\fIfree\fR().

For

\fIrealpath\fR(),

this is the return value.

.SH RATIONALE

Since

\fIrealpath\fR()

has no

.IR length

argument, if

{PATH_MAX}

is not defined as a constant in

.IR <limits.h> ,

applications have no way of determining how large a buffer they need

to allocate for it to be safe to pass to

\fIrealpath\fR().

A

{PATH_MAX}

value obtained from a prior

\fIpathconf\fR()

call is out-of-date by the time

\fIrealpath\fR()

is called. Hence the only reliable way to use

\fIrealpath\fR()

when

{PATH_MAX}

is not defined in

.IR <limits.h> 

is to pass a null pointer for

.IR resolved_name

so that

\fIrealpath\fR()

will allocate a buffer of the necessary size.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.IR "\fIfpathconf\fR\^(\|)",

.IR "\fIfree\fR\^(\|)",

.IR "\fIgetcwd\fR\^(\|)",

.IR "\fIsysconf\fR\^(\|)"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<limits.h>\fP",

.IR "\fB<stdlib.h>\fP"

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 7, Copyright (C) 2013 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group.

(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the

event of any discrepancy between this version and the original IEEE and

The Open Group Standard, the original IEEE and The Open Group Standard

is the referee document. The original Standard can be obtained online at

http://www.unix.org/online.html .

Any typographical or formatting errors that appear

in this page are most likely

to have been introduced during the conversion of the source files to

man page format. To report such errors, see

https://www.kernel.org/doc/man-pages/reporting_bugs.html .