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tmpnam(3p) [centos man page]

TMPNAM(3P)						     POSIX Programmer's Manual							TMPNAM(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
tmpnam - create a name for a temporary file SYNOPSIS
#include <stdio.h> char *tmpnam(char *s); DESCRIPTION
The tmpnam() function shall generate a string that is a valid filename and that is not the same as the name of an existing file. The func- tion is potentially capable of generating {TMP_MAX} different strings, but any or all of them may already be in use by existing files and thus not be suitable return values. The tmpnam() function generates a different string each time it is called from the same process, up to {TMP_MAX} times. If it is called more than {TMP_MAX} times, the behavior is implementation-defined. The implementation shall behave as if no function defined in this volume of IEEE Std 1003.1-2001 calls tmpnam(). If the application uses any of the functions guaranteed to be available if either _POSIX_THREAD_SAFE_FUNCTIONS or _POSIX_THREADS is defined, the application shall ensure that the tmpnam() function is called with a non-NULL parameter. RETURN VALUE
Upon successful completion, tmpnam() shall return a pointer to a string. If no suitable string can be generated, the tmpnam() function shall return a null pointer. If the argument s is a null pointer, tmpnam() shall leave its result in an internal static object and return a pointer to that object. Sub- sequent calls to tmpnam() may modify the same object. If the argument s is not a null pointer, it is presumed to point to an array of at least L_tmpnam chars; tmpnam() shall write its result in that array and shall return the argument as its value. ERRORS
No errors are defined. The following sections are informative. EXAMPLES
Generating a Filename The following example generates a unique filename and stores it in the array pointed to by ptr. #include <stdio.h> ... char filename[L_tmpnam+1]; char *ptr; ptr = tmpnam(filename); APPLICATION USAGE
This function only creates filenames. It is the application's responsibility to create and remove the files. Between the time a pathname is created and the file is opened, it is possible for some other process to create a file with the same name. Applications may find tmpfile() more useful. RATIONALE
None. FUTURE DIRECTIONS
None. SEE ALSO
fopen(), open(), tempnam(), tmpfile(), unlink(), the Base Definitions volume of IEEE Std 1003.1-2001, <stdio.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol- ogy -- 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 . IEEE
/The Open Group 2003 TMPNAM(3P)

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TMPNAM(3)						     Linux Programmer's Manual							 TMPNAM(3)

NAME
tmpnam, tmpnam_r - create a name for a temporary file SYNOPSIS
#include <stdio.h> char *tmpnam(char *s); DESCRIPTION
The tmpnam() function returns a pointer to a string that is a valid filename, and such that a file with this name did not exist at some point in time, so that naive programmers may think it a suitable name for a temporary file. If the argument s is NULL this name is gener- ated in an internal static buffer and may be overwritten by the next call to tmpnam(). If s is not NULL, the name is copied to the charac- ter array (of length at least L_tmpnam) pointed to by s and the value s is returned in case of success. The pathname that is created, has a directory prefix P_tmpdir. (Both L_tmpnam and P_tmpdir are defined in <stdio.h>, just like the TMP_MAX mentioned below.) RETURN VALUE
The tmpnam() function returns a pointer to a unique temporary filename, or NULL if a unique name cannot be generated. ERRORS
No errors are defined. CONFORMING TO
SVr4, 4.3BSD, C89, C99, POSIX.1-2001. POSIX.1-2008 marks tmpnam() as obsolete. NOTES
The tmpnam() function generates a different string each time it is called, up to TMP_MAX times. If it is called more than TMP_MAX times, the behavior is implementation defined. Although tmpnam() generates names that are difficult to guess, it is nevertheless possible that between the time that tmpnam() returns a pathname, and the time that the program opens it, another program might create that pathname using open(2), or create it as a symbolic link. This can lead to security holes. To avoid such possibilities, use the open(2) O_EXCL flag to open the pathname. Or better yet, use mkstemp(3) or tmpfile(3). Portable applications that use threads cannot call tmpnam() with a NULL argument if either _POSIX_THREADS or _POSIX_THREAD_SAFE_FUNCTIONS is defined. A POSIX draft proposed to use a function tmpnam_r() defined by char * tmpnam_r(char *s) { return s ? tmpnam(s) : NULL; } apparently as a warning not to use NULL. A few systems implement it. To get a glibc prototype for this function from <stdio.h>, define _SVID_SOURCE or _BSD_SOURCE (before including any header file). BUGS
Never use this function. Use mkstemp(3) or tmpfile(3) instead. SEE ALSO
mkstemp(3), mktemp(3), tempnam(3), tmpfile(3) COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2010-09-10 TMPNAM(3)
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