Get file name from FILE * returned from mkstemp

Question

I have some code that looks like this:

char template[] = "temp-XXXXXX";
FILE * f = mkstmp(template);

/* ... some stuff is written to f with fprintf ...*/

char fname[15] = xyzzy(f); // <-- Problem

char tmp[20];
sprintf(tmp,"less %s", fname);
system(tmp);

I need to find out the name given to f by mkstmp so I can call less on it.

I think you should self answer your question, so if someone finds your question in the future, ho would also find the answer (and maybe you would earn some rep :-) ) — Ingo Leonhardt, Jun 08 '16 at 18:44
Possible duplicate of [Obtain filename from file pointer in C](http://stackoverflow.com/questions/9937645/obtain-filename-from-file-pointer-in-c) — ebyrob, Jun 08 '16 at 18:44
@ebyrob not quite, because while in the general case it's not possible (in a portable way at least), in the special case of using `mkstmp()` it's easy — Ingo Leonhardt, Jun 08 '16 at 18:46
No, `mkstemp` (not `mkstmp`) returns an `int`. I don't know of *any* library function that returns a `FILE`. — Keith Thompson, Jun 09 '16 at 16:21
@KeithThompson from the mkstemp man page: "On success, these functions return the file descriptor of the temporary file. On error, -1 is returned, and errno is set appropriately." — SIGSTACKFAULT, Jun 09 '16 at 17:18
@Blacksilver File descriptors are integers. Read `man 2 open`, `man 2 write`. — n. m. could be an AI, Jun 09 '16 at 17:35
@Blacksilver: And if you need a `FILE*`, you can pass the file descriptor to `fdopen`. — Keith Thompson, Jun 09 '16 at 17:56

SIGSTACKFAULT · Accepted Answer · 2017-05-19T17:30:29.983

1

template will have been changed to the file's name. So:

sprintf(tmp,"less %s",template)
system(tmp);

edited May 19 '17 at 17:30

answered Jun 09 '16 at 14:30

SIGSTACKFAULT

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You should place your answer here and accept that. Do not place the answer in your question. – Rob Jun 09 '16 at 14:34
@rob This is here for the benefit of people who scroll right past the question. – SIGSTACKFAULT Jun 09 '16 at 15:54

Get file name from FILE * returned from mkstemp

1 Answers1