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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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REALPATH(3P) POSIX Programmer's Manual REALPATH(3P)
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.
realpath — resolve a pathname
#include <stdlib.h>
char *realpath(const char *restrict file_name,
char *restrict resolved_name);
The realpath() function shall derive, from the pathname pointed to by
file_name, an absolute pathname that resolves to the same directory
entry, whose resolution does not involve '.', '..', or symbolic
links. If 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 malloc(). Otherwise, if {PATH_MAX} is defined as a
constant in the <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 resolved_name.
If resolved_name is not a null pointer and {PATH_MAX} is not defined
as a constant in the <limits.h> header, the behavior is undefined.
Upon successful completion, realpath() shall return a pointer to the
buffer containing the resolved name. Otherwise, realpath() shall
return a null pointer and set errno to indicate the error.
If the resolved_name argument is a null pointer, the pointer returned
by realpath() can be passed to free().
If the resolved_name argument is not a null pointer and the
realpath() function fails, the contents of the buffer pointed to by
resolved_name are undefined.
The realpath() function shall fail if:
EACCES Search permission was denied for a component of the path
prefix of file_name.
EINVAL The file_name argument is a null pointer.
EIO An error occurred while reading from the file system.
ELOOP A loop exists in symbolic links encountered during resolution
of the file_name argument.
ENAMETOOLONG
The length of a component of a pathname is longer than
{NAME_MAX}.
ENOENT A component of file_name does not name an existing file or
file_name points to an empty string.
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
file_name argument contains at least one non-<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.
The realpath() function may fail if:
EACCES The file_name argument does not begin with a <slash> and none
of the symbolic links (if any) processed during pathname
resolution of 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.
ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
resolution of the file_name argument.
ENAMETOOLONG
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}.
ENOMEM Insufficient storage space is available.
The following sections are informative.
Generating an Absolute Pathname
The following example generates an absolute pathname for the file
identified by the symlinkpath argument. The generated pathname is
stored in the buffer pointed to by actualpath.
#include <stdlib.h>
...
char *symlinkpath = "/tmp/symlink/file";
char *actualpath;
actualpath = realpath(symlinkpath, NULL);
if (actualpath != NULL)
{
... use actualpath ...
free(actualpath);
}
else
{
... handle error ...
}
For functions that allocate memory as if by malloc(), the application
should release such memory when it is no longer required by a call to
free(). For realpath(), this is the return value.
Since realpath() has no length argument, if {PATH_MAX} is not defined
as a constant in <limits.h>, applications have no way of determining
how large a buffer they need to allocate for it to be safe to pass to
realpath(). A {PATH_MAX} value obtained from a prior pathconf() call
is out-of-date by the time realpath() is called. Hence the only
reliable way to use realpath() when {PATH_MAX} is not defined in
<limits.h> is to pass a null pointer for resolved_name so that
realpath() will allocate a buffer of the necessary size.
None.
fpathconf(3p), free(3p), getcwd(3p), sysconf(3p)
The Base Definitions volume of POSIX.1‐2008, limits.h(0p),
stdlib.h(0p)
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 .
IEEE/The Open Group 2013 REALPATH(3P)
Pages that refer to this page: stdlib.h(0p)
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