realpath(3) [osx man page]
REALPATH(3) BSD Library Functions Manual REALPATH(3) NAME
realpath -- returns the canonicalized absolute pathname SYNOPSIS
#include <stdlib.h> char * realpath(const char *restrict file_name, char *restrict resolved_name); DESCRIPTION
The realpath() function resolves all symbolic links, extra ``/'' characters, and references to /./ and /../ in file_name. If the resolved_name argument is non-NULL, the resulting absolute pathname is copied there (it must refer to a buffer capable of storing at least PATH_MAX characters). As a permitted extension to the standard, if resolved_name is NULL, memory is allocated for the resulting absolute pathname, and is returned by realpath(). This memory should be freed by a call to free(3) when no longer needed. The realpath() function will resolve both absolute and relative paths and return the absolute pathname corresponding to file_name. All com- ponents of file_name must exist when realpath() is called. RETURN VALUES
On success, the realpath() function returns the address of the resulting absolute pathname, which is resolved_name if it was non-NULL, or the address of newly allocated memory. If an error occurs, realpath() returns NULL. If resolved_name was non-NULL, it will contains the path- name which caused the problem. VARIANTS
Defining _DARWIN_C_SOURCE or _DARWIN_BETTER_REALPATH before including stdio.h will cause the provided implementation of realpath() to use F_GETPATH from fcntl(2) to discover the path. ERRORS
The function realpath() may fail and set the external variable errno for any of the errors specified for the library functions alloca(3), getattrlist(2), getcwd(3), lstat(2), readlink(2), stat(2), and strdup(3). LEGACY SYNOPSIS
#include <sys/param.h> #include <stdlib.h> The include file <sys/param.h> is necessary. LEGACY DESCRIPTION
In legacy mode, the last component of file_name does not need to exist when realpath() is called. SEE ALSO
free(3), getcwd(3), compat(5) HISTORY
The realpath() function first appeared in 4.4BSD. BSD
April 5, 2008 BSD
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REALPATH(3P) POSIX Programmer's Manual REALPATH(3P) PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond- ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. 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 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. RETURN VALUE
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. ERRORS
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. 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 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 ... } APPLICATION USAGE
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. RATIONALE
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. FUTURE DIRECTIONS
None. SEE ALSO
fpathconf(), free(), getcwd(), sysconf() The Base Definitions volume of POSIX.1-2008, <limits.h>, <stdlib.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technol- ogy -- 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 Stan- dard 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)