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PROLOG |NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |EXAMPLES |APPLICATION USAGE |RATIONALE |FUTURE DIRECTIONS |SEE ALSO |COPYRIGHT | |
REALPATH(3P) POSIX Programmer's ManualREALPATH(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 *restrictfile_name, char *restrictresolved_name);
Therealpath() function shall derive, from the pathname pointed to byfile_name, an absolute pathname that resolves to the same directory entry, whose resolution does not involve'.','..', or symbolic links. Ifresolved_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 tomalloc(). 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 byresolved_name. Ifresolved_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 seterrno to indicate the error. If theresolved_name argument is a null pointer, the pointer returned byrealpath() can be passed tofree(). If theresolved_name argument is not a null pointer and therealpath() function fails, the contents of the buffer pointed to byresolved_name are undefined.
Therealpath() function shall fail if:EACCESSearch permission was denied for a component of the path prefix offile_name.EINVALThefile_name argument is a null pointer.EIOAn error occurred while reading from the file system.ELOOPA loop exists in symbolic links encountered during resolution of thefile_name argument.ENAMETOOLONG The length of a component of a pathname is longer than {NAME_MAX}.ENOENTA component offile_name does not name an existing file orfile_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 thefile_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. Therealpath() function may fail if:EACCESThefile_name argument does not begin with a <slash> and none of the symbolic links (if any) processed during pathname resolution offile_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.ELOOPMore than {SYMLOOP_MAX} symbolic links were encountered during resolution of thefile_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}.ENOMEMInsufficient 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 thesymlinkpath argument. The generated pathname is stored in the buffer pointed to byactualpath. #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 bymalloc(), the application should release such memory when it is no longer required by a call tofree(). Forrealpath(), this is the return value.
Sincerealpath() has nolength 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 torealpath(). A {PATH_MAX} value obtained from a priorpathconf() call is out-of-date by the timerealpath() is called. Hence the only reliable way to userealpath() when {PATH_MAX} is not defined in<limits.h> is to pass a null pointer forresolved_name so thatrealpath() will allocate a buffer of the necessary size.None.
fpathconf(3p),free(3p),getcwd(3p),sysconf(3p) The Base Definitions volume of POSIX.1‐2017,limits.h(0p),stdlib.h(0p)
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 athttp://www.opengroup.org/unix/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, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group 2017REALPATH(3P)Pages that refer to this page:stdlib.h(0p)
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