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@(#)mktemp.3 8.1 (Berkeley) 6/4/93
.Dd July 28, 1998 .Dt MKTEMP 3 .Os .Sh NAME .Nm mktemp , .Nm mkstemp , .Nm mkdtemp .Nd make unique temporary file or directory name .Sh LIBRARY .Lb libc .Sh SYNOPSIS .Fd #include \*[Lt]stdlib.h\*[Gt] .Ft char * .Fn mktemp "char *template" .Ft int .Fn mkstemp "char *template" .Ft char * .Fn mkdtemp "char *template" .Sh DESCRIPTION The .Fn mktemp function takes the given file name template and overwrites a portion of it to create a file name. This file name is unique and suitable for use by the application. The template may be any file name with some number of .Ql X Ns s appended to it, for example
a /tmp/temp.XXXX . The trailing .Ql X Ns s are replaced with the current process number and/or a unique letter combination. The number of unique file names .Fn mktemp can return depends on the number of .Ql X Ns s provided; six .Ql X Ns s will result in .Fn mktemp testing roughly 26 ** 6 combinations.
p The .Fn mkstemp function makes the same replacement to the template and creates the template file, mode 0600, returning a file descriptor opened for reading and writing. This avoids the race between testing for a file's existence and opening it for use.
p The .Fn mkdtemp function is similar to .Fn mkstemp , but it creates a mode 0700 directory instead and returns the path.
p Please note that the permissions of the file or directory being created are subject to the restrictions imposed by the .Xr umask 2 system call. It may thus happen that the created file is unreadable and/or unwritable. .Sh RETURN VALUES The .Fn mktemp and .Fn mkdtemp functions return a pointer to the template on success and .Dv NULL on failure. The .Fn mkstemp function returns -1 if no suitable file could be created. If either call fails an error code is placed in the global variable .Va errno . .Sh ERRORS The .Fn mktemp , .Fn mkstemp and .Fn mkdtemp functions may set .Va errno to one of the following values: l -tag -width Er t Bq Er ENOTDIR The pathname portion of the template is not an existing directory. .El
p The .Fn mktemp , .Fn mkstemp and .Fn mkdtemp functions may also set .Va errno to any value specified by the .Xr stat 2 function.
p The .Fn mkstemp function may also set .Va errno to any value specified by the .Xr open 2 function.
p The .Fn mkdtemp function may also set .Va errno to any value specified by the .Xr mkdir 2 function. .Sh SEE ALSO .Xr chmod 2 , .Xr getpid 2 , .Xr open 2 , .Xr stat 2 , .Xr umask 2 .Sh HISTORY A .Fn mktemp function appeared in .At v7 .
p The .Fn mkstemp function appeared in x 4.4 .
p The .Fn mkdtemp function appeared in .Nx 1.4 . .Sh SECURITY CONSIDERATIONS The use of .Fn mktemp should generally be avoided, as a hostile process can exploit a race condition in the time between the generation of a temporary filename by .Fn mktemp and the invoker's use of the temporary name. A link-time warning will be issued advising the use of .Fn mkstemp or .Fn mkdtemp instead.