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NAME
realpath - resolve a pathname
SYNOPSIS
#include <stdlib.h> char *realpath(const char *restrict file_name, char *restrict resolved_name);
DESCRIPTION
The realpath() function shall derive, from the pathname pointed to by file_name, an absolute pathname
that names the same file, whose resolution does not involve '.' , '..' , or symbolic links. 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 a null pointer, the behavior of realpath() is implementation-defined.
RETURN VALUE
Upon successful completion, realpath() shall return a pointer to the resolved name. Otherwise, realpath()
shall return a null pointer and set errno to indicate the error, and the contents of the buffer pointed
to by resolved_name are undefined.
ERRORS
The realpath() function shall fail if:
EACCES Read or search permission was denied for a component 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 path argument.
ENAMETOOLONG
The length of the file_name argument exceeds {PATH_MAX} or a pathname component 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 is not a directory.
The realpath() function may fail if:
ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.
ENAMETOOLONG
Pathname resolution of a symbolic link produced an intermediate result whose length exceeds
{PATH_MAX}.
ENOMEM Insufficient storage space is available.
The following sections are informative.
EXAMPLES
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 actualpath array.
#include <stdlib.h>
...
char *symlinkpath = "/tmp/symlink/file";
char actualpath [PATH_MAX+1];
char *ptr;
ptr = realpath(symlinkpath, actualpath);
APPLICATION USAGE
None.
RATIONALE
Since the maximum pathname length is arbitrary unless {PATH_MAX} is defined, an application generally
cannot supply a resolved_name buffer with size {{PATH_MAX}+1}.
FUTURE DIRECTIONS
In the future, passing a null pointer to realpath() for the resolved_name argument may be defined to have
realpath() allocate space for the generated pathname.
SEE ALSO
getcwd() , sysconf() , the Base Definitions volume of IEEE Std 1003.1-2001, <stdlib.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. 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.opengroup.org/unix/online.html .