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mktemp(3) [linux man page]

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

NAME
mktemp - make a unique temporary filename SYNOPSIS
#include <stdlib.h> char *mktemp(char *template); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): mktemp(): Since glibc 2.12: _BSD_SOURCE || _SVID_SOURCE || (_XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) && !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) Before glibc 2.12: _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED DESCRIPTION
The mktemp() function generates a unique temporary filename from template. The last six characters of template must be XXXXXX and these are replaced with a string that makes the filename unique. Since it will be modified, template must not be a string constant, but should be declared as a character array. RETURN VALUE
The mktemp() function always returns template. If a unique name was created, the last six bytes of template will have been modified in such a way that the resulting name is unique (i.e., does not exist already) If a unique name could not be created, template is made an empty string. ERRORS
EINVAL The last six characters of template were not XXXXXX. CONFORMING TO
4.3BSD, POSIX.1-2001. POSIX.1-2008 removes the specification of mktemp(). NOTES
The prototype is in <unistd.h> for libc4, libc5, glibc1; glibc2 follows the Single Unix Specification and has the prototype in <stdlib.h>. BUGS
Never use mktemp(). Some implementations follow 4.3BSD and replace XXXXXX by the current process ID and a single letter, so that at most 26 different names can be returned. Since on the one hand the names are easy to guess, and on the other hand there is a race between test- ing whether the name exists and opening the file, every use of mktemp() is a security risk. The race is avoided by mkstemp(3). SEE ALSO
mkstemp(3), tempnam(3), tmpfile(3), tmpnam(3) COLOPHON
This page is part of release 3.27 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/. GNU
2010-09-20 MKTEMP(3)

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

NAME
mkstemp, mkostemp - create a unique temporary file SYNOPSIS
#include <stdlib.h> int mkstemp(char *template); int mkostemp (char *template, int flags); int mkstemps(char *template, int suffixlen); int mkostemps(char *template, int suffixlen, int flags); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): mkstemp(): Since glibc 2.12: _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600 Before glibc 2.12: _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED mkostemp(): _GNU_SOURCE mkstemps(): _BSD_SOURCE || _SVID_SOURCE mkostemps(): _GNU_SOURCE DESCRIPTION
The mkstemp() function generates a unique temporary filename from template, creates and opens the file, and returns an open file descriptor for the file. The last six characters of template must be "XXXXXX" and these are replaced with a string that makes the filename unique. Since it will be modified, template must not be a string constant, but should be declared as a character array. The file is created with permissions 0600, that is, read plus write for owner only. (In glibc versions 2.06 and earlier, the file is cre- ated with permissions 0666, that is, read and write for all users.) The returned file descriptor provides both read and write access to the file. The file is opened with the open(2) O_EXCL flag, guaranteeing that the caller is the process that creates the file. The mkostemp() function is like mkstemp(), with the difference that flags as for open(2) may be specified in flags (e.g., O_APPEND, O_SYNC). The mkstemps() function is like mkstemp(), except that the string in template contains a suffix of suffixlen characters. Thus, template is of the form prefixXXXXXXsuffix, and the string XXXXXX is modified as for mkstemp(). The mkostemps() function is to mkstemps() as mkostemp() is to mkstemp(). RETURN VALUE
On success, these functions return the file descriptor of the temporary file. On error, -1 is returned, and errno is set appropriately. ERRORS
EEXIST Could not create a unique temporary filename. Now the contents of template are undefined. EINVAL For mkstemp() and mkostemp(): The last six characters of template were not XXXXXX; now template is unchanged. For mkstemps() and mkostemps() template is less than (6 + suffixlen) characters long, or the last 6 characters before the suffix in template were not XXXXXX. These functions may also fail with any of the errors described for open(2). VERSIONS
mkostemp() is available since glibc 2.7. mkstemps() and mkostemps() are available since glibc 2.11. CONFORMING TO
mkstemp(): 4.3BSD, POSIX.1-2001. mkstemps(): unstandardized, but appears on several other systems. mkostemp() and mkostemps(): are glibc extensions. NOTES
The old behavior of creating a file with mode 0666 may be a security risk, especially since other Unix flavors use 0600, and somebody might overlook this detail when porting programs. More generally, the POSIX specification of mkstemp() does not say anything about file modes, so the application should make sure its file mode creation mask (see umask(2)) is set appropriately before calling mkstemp() (and mkostemp()). The prototype for mktemp() is in <unistd.h> for libc4, libc5, glibc1; glibc2 follows POSIX.1 and has the prototype in <stdlib.h>. SEE ALSO
mkdtemp(3), mktemp(3), tempnam(3), tmpfile(3), tmpnam(3) COLOPHON
This page is part of release 3.27 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/. GNU
2010-09-20 MKSTEMP(3)

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