MKSTEMP Section: Linux Programmer's Manual (3) Updated: April 3, 2025 Index   NAME mkstemp - create a unique temporary file   SYNOPSIS #include <stdlib.h> int mkstemp(char *template);   DESCRIPTION The mkstemp() function generates a unique temporary file name from template. The last six characters of template must be XXXXXX and these are replaced with a string that makes the filename unique. The file is then created with mode read/write and permissions 0666 (glibc 2.0.6 and earlier), 0600 (glibc 2.0.7 and later). Since it will be modified, template must not be a string constant, but should be declared as a character array. The file is opened with the O_EXCL flag, guaranteeing that when mkstemp returns successfully we are the only user.   RETURN VALUE The mkstemp() function returns the file descriptor fd of the temporary file or -1 on error.   ERRORS EINVAL The last six characters of template were not XXXXXX. Now template is unchanged. EEXIST Could not create a unique temporary filename. Now the contents of template are undefined.   BUGS The old behaviour (creating a file with mode 0666) may be a security risk, especially since other Unix flavours use 0600, and somebody might overlook this detail when porting programs.   CONFORMING TO BSD 4.3   NOTE The prototype is in <unistd.h> for libc4, libc5, glibc1; glibc2 follows the Single Unix Specification and has the prototype in <stdlib.h>.   SEE ALSO   Index NAME SYNOPSIS DESCRIPTION RETURN VALUE ERRORS BUGS CONFORMING TO NOTE SEE ALSO This document was created by using the manual pages. Time: 11:58:05 GMT, March 24, 2025