| .\" Copyright (C) 1999 Andries Brouwer (aeb@cwi.nl) |
| .\" |
| .\" Permission is granted to make and distribute verbatim copies of this |
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| .\" manual page may be incorrect or out-of-date. The author(s) assume no |
| .\" responsibility for errors or omissions, or for damages resulting from |
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| .\" which is licensed free of charge, as they might when working |
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| .\" Rewritten old page, 990824, aeb@cwi.nl |
| .\" 2004-12-14, mtk, added discussion of resolved_path == NULL |
| .\" |
| .TH REALPATH 3 2004-12-14 "" "Linux Programmer's Manual" |
| .SH NAME |
| realpath \- return the canonicalized absolute pathname |
| .SH SYNOPSIS |
| .nf |
| .B #include <limits.h> |
| .B #include <stdlib.h> |
| .sp |
| .BI "char *realpath(const char *" path ", char *" resolved_path ); |
| .SH DESCRIPTION |
| .BR realpath () |
| expands all symbolic links and resolves references |
| to |
| .IR '/./' ", " '/../' |
| and extra |
| .I '/' |
| characters in the null terminated string named by |
| .I path |
| and stores the canonicalized absolute pathname in the buffer of size |
| .B PATH_MAX |
| named by |
| .IR resolved_path . |
| The resulting path will have no symbolic link, |
| .I '/./' |
| or |
| .I '/../' |
| components. |
| .SH "RETURN VALUE" |
| If there is no error, |
| .BR realpath () |
| returns a pointer to the |
| .IR resolved_path . |
| |
| Otherwise it returns a NULL pointer, and the contents |
| of the array |
| .I resolved_path |
| are undefined. The global variable |
| .I errno |
| is set to indicate the error. |
| .SH ERRORS |
| .TP |
| .B EACCES |
| Read or search permission was denied for a component of the path prefix. |
| .TP |
| .B EINVAL |
| Either |
| .I path |
| or |
| .I resolved_path |
| is NULL. (In libc5 this would just cause a segfault.) |
| But, see NOTES below. |
| .TP |
| .B EIO |
| An I/O error occurred while reading from the file system. |
| .TP |
| .B ELOOP |
| Too many symbolic links were encountered in translating the pathname. |
| .TP |
| .B ENAMETOOLONG |
| A component of a path name exceeded |
| .B NAME_MAX |
| characters, or an entire path name exceeded |
| .B PATH_MAX |
| characters. |
| .TP |
| .B ENOENT |
| The named file does not exist. |
| .TP |
| .B ENOTDIR |
| A component of the path prefix is not a directory. |
| .SH NOTES |
| The glibc implementation of |
| .BR realpath () |
| provides a non-standard extension. |
| If |
| .I resolved_path |
| is specified as NULL, then |
| .BR realpath () |
| uses |
| .BR malloc (3) |
| to allocate a buffer of up to PATH_MAX bytes |
| to hold the resolved pathname, |
| and returns a pointer to this buffer. |
| The caller should deallocate this buffer using |
| .BR free (3). |
| .\" Even if we use resolved_path == NULL, then realpath() will still |
| .\" return ENAMETOOLONG if the resolved pathname would exceed PATH_MAX |
| .\" bytes -- MTK, Dec 04 |
| .SH BUGS |
| Avoid using this function. It is broken by design since (unless |
| using the non-standard |
| .I "resolved_path\ ==\ NULL" |
| feature) it is |
| impossible to determine a suitable size for the output buffer, |
| .IR resolved_path . |
| According to POSIX a buffer of size PATH_MAX suffices, but |
| PATH_MAX need not be a defined constant, and may have to be |
| obtained using |
| .BR pathconf (). |
| And asking |
| .BR pathconf () |
| does not really help, since on the one hand POSIX warns that |
| the result of |
| .BR pathconf () |
| may be huge and unsuitable for mallocing memory. And on the other |
| hand |
| .BR pathconf () |
| may return \-1 to signify that PATH_MAX is not bounded. |
| .LP |
| The libc4 and libc5 implementation contains a buffer overflow |
| (fixed in libc-5.4.13). |
| Thus, set-user-ID programs like mount need a private version. |
| .SH HISTORY |
| The |
| .BR realpath () |
| function first appeared in 4.4BSD, contributed by Jan-Simon Pendry. |
| In Linux this function appears in libc 4.5.21. |
| .SH "CONFORMING TO" |
| In 4.4BSD and Solaris the limit on the pathname length is MAXPATHLEN |
| (found in <sys/param.h>). The SUSv2 prescribes PATH_MAX and |
| NAME_MAX, as found in <limits.h> or provided by the |
| .BR pathconf () |
| function. A typical source fragment would be |
| .LP |
| .RS |
| .nf |
| #ifdef PATH_MAX |
| path_max = PATH_MAX; |
| #else |
| path_max = pathconf (path, _PC_PATH_MAX); |
| if (path_max <= 0) |
| path_max = 4096; |
| #endif |
| .fi |
| .RE |
| (But see the BUGS section.) |
| .LP |
| The 4.4BSD, Linux and SUSv2 versions always return an absolute |
| path name. Solaris may return a relative path name when the |
| .I path |
| argument is relative. |
| The prototype of |
| .BR realpath () |
| is given in <unistd.h> in libc4 and libc5, |
| but in <stdlib.h> everywhere else. |
| .SH "SEE ALSO" |
| .BR readlink (2), |
| .BR canonicalize_file_name (3), |
| .BR getcwd (3), |
| .BR pathconf (3), |
| .BR sysconf (3) |