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warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘__dev_t’ [-Wformat=]

I am using stat file system in a program and I want to print the device id using

printf("\nst_dev = %s\n",buf.st_dev);

but i am getting error:

warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘__dev_t’ [-Wformat=]

What should b used instead of %s here?

Solution

  • st_dev is of type dev_t which is an integer type as per POSIX definition:

    dev_t shall be an integer type.

    So printing it using %s certainly wrong. There's no portable way to print it because there's no format specifier defined for it in POSIX. You could use intmax_t to print it:

    printf("\nst_dev = %jd\n", (intmax_t)buf.st_dev);

    If intmax_t isn't available (such as C89 systems) then you could cast it to long.