StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
text
Body
copied!<pre><code>/* * TODO: write manpage */ #include <assert.h> #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #define ERROR_MAX 2048 /* arbitrary, must account for argv[0] */ #define MSG_SIZE (5+9+1) /* +1 for newline, +1 for NUL */ #if defined(linux) || defined(BSD) && BSD > 199300L extern char const *__progname; # define progname __progname #else static char *progname; #endif typedef enum _Progerr { IO_ERR = 1, RND_ERR = 2 } progerr_t; static const char GREET_START[5] = "Good"; /* XXX move to Makefile? */ static const char *TIMES_OF_DAY[5] = { "Morning", "Afternoon", "Evening", "Night", NULL }; int main() { char errbuf[ERROR_MAX]; char msgbuf[MSG_SIZE]; char *slash; const char **time_of_day; int fd, rnd; size_t greet_len; #ifndef progname /* we want proper error messages */ progname = argv[0]; if ((slash = strrchr(progname, '/')) != NULL) progname = slash+1; #endif /* get REAL randomness; can't trust rand(3). * avoid stdio, it's slow. */ #ifdef DEBUG write(STDERR_FILENO, "getting random data\n", sizeof("getting random data\n")-1); #endif if ((fd = open("/dev/urandom", O_RDONLY)) == -1) { if ((fd = open("/dev/random", O_RDONLY)) == -1) rnd = rand(); /* last resort, for MSYS etc. */ } if (fd >= 0 && read(fd, &rnd, sizeof(int)) != sizeof(int)) { close(fd); goto rngerr; } /* higher bits of rand() have better entropy */ assert(sizeof(int) >= 4); /* should be compile-time assert */ rnd = (rnd >> 24) & 0x03; for (time_of_day = TIMES_OF_DAY; *time_of_day && rnd; time_of_day++, rnd--) ; if (!time_of_day) goto rngerr; sprintf(msgbuf, "%s %s", GREET_START, *time_of_day); greet_len = strlen(msgbuf); msgbuf[greet_len] = '\n'; if (write(STDOUT_FILENO, msgbuf, greet_len+1) == -1) goto write_err; return 0; rngerr: sprintf(errbuf, "%s: cannot get random data\n", progname); write(STDERR_FILENO, errbuf, strlen(errbuf)); return (int)RND_ERR; write_err: sprintf(errbuf, "%s: cannot write to stdout\n", progname); write(STDERR_FILENO, errbuf, strlen(errbuf)); return (int)IO_ERR; } </code></pre>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload