NAME

mktemp, mkstemp − make a unique file name

SYNOPSIS

char ∗mktemp(template)
char ∗template;

mkstemp(template)
char ∗template;

DESCRIPTION

mktemp() creates a unique file name, typically in a temporary filesystem, by replacing template with a unique file name, and returns the address of template. The string in template should contain a file name with six trailing Xs; mktemp() replaces the Xs with a letter and the current process ID.  The letter will be chosen so that the resulting name does not duplicate an existing file.  mkstemp() makes the same replacement to the template but returns a file descriptor for the template file open for reading and writing.  mkstemp() avoids the race between testing whether the file exists and opening it for use. 

Notes:

• mktemp() and mkstemp() actually change the template string which you pass; this means that you cannot use the same template string more than once — you need a fresh template for every unique file you want to open. 

• When mktemp() or mkstemp() are creating a new unique filename they check for the prior existence of a file with that name.  This means that if you are creating more than one unique filename, it is bad practice to use the same root template for multiple invocations of mktemp() or mkstemp(). 

SEE ALSO

getpid(2V), open(2V), tmpfile(3S), tmpnam(3S)

DIAGNOSTICS

mkstemp() returns an open file descriptor upon success.  It returns −1 if no suitable file could be created. 

mktemp() assigns the null string to template when it cannot create a unique name. 

BUGS

It is possible to run out of letters. 

Solbourne Computer, Inc.  —  6 September 1989