wtmpnam

Name

wtmpnam - generate temporary file name.

Library

libc.lib

Synopsis

#include <wchar.h>

wchar_t * wtmpnam (wchar_t *str);

Return values

The wtmpnam function return a pointer to a file name on success, and a NULL pointer on error.

Detailed description

The wtmpnam function returns a pointer to a file name, in the P_tmpdir directory, which did not reference an existing file at some indeterminate point in the past. P_tmpdir is defined in the include file stdio.h. If the argument str is non-NULL, the file name is copied to the buffer it references. Otherwise, the file name is copied to a static buffer. In either case, wtmpnam returns a pointer to the file name.

The buffer referenced by str is expected to be at least L_tmpnam bytes in length. L_tmpnam is defined in the include file stdio.h.

The environment variable TMPDIR (if set), the argument tmpdir (if non-NULL), the directory P_tmpdir, and the directory /tmp are tried, in the listed order, as directories in which to store the temporary file.

Examples

#include<stdio.h> //wtmpnam
#include<sys/stat.h> //S_IWUSR
#include<errno.h> //errno
  
int main()
{
 //create a directory c:\system emp
 wmkdir(L"c:\\system\\temp", S_IWUSR);
  
 wchar_t wbuf[L_tmpnam];
 wchar_t rbuf[10];
  
 //call wtmpnam() to create a file
 wchar_t *rval = wtmpnam(wbuf);
  
 errno = 0;
 //open the file with the name returned by wtmpnam()
 FILE *fp = wfopen(buf, L"w");
  
 if (fp == NULL)
 {
     printf("fopen of file returned by wtmpnam() failed - errno %d ", errno);
     return -1;
 }
    
 if(fp)
 {
    fwprintf(fp, L"%ls", L"check");
    fclose(fp);
 }
   
 fp = wfopen(buf, L"r");
  
 if(fp)
 {
     fwscanf(fp, L"%ls", rbuf);
     fclose(fp);
 }
  
 printf("read from file: %ls\n", rbuf);
 printf("argument buf: %ls\n", buf);
 printf("return value: %ls\n", rval);
  
 return 0;
}

Output

read from file: check
argument buf: /System/temp/tmp.0.U9UPTx
return value: /System/temp/tmp.0.U9UPTx

Errors

The wtmpnam function may fail and set errno for any of the errors specified for the library function mktemp.

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