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#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
static char *
get_tty_name(void)
{ /* Returns the name of the tty connected to the file descriptor for
`stdin'. */
return ttyname(STDIN_FILENO);
}
static char *
get_filename(void)
{ /* Generate the filename to be used for the current tty. Uses both
the user ID of the calling user and the name of the current tty
to make it unique. */
char *filename = malloc(sizeof(char) * 255);
char *tty = get_tty_name();
char *pch;
while ((pch = strchr(tty, '/')))
*pch = '_';
sprintf(filename, "/tmp/baps1_%u_%s", getuid(), tty);
return filename;
}
static time_t
load_previous_time(char *filename)
{ /* Loads the previously saved timestamp from FILENAME. This function
assumes the file exists and is readable. */
FILE *timefile = fopen(filename, "r");
time_t prev;
fscanf(timefile, "%ld", &prev);
fclose(timefile);
return prev;
}
static time_t
get_previous_time(char *filename)
{ /* Tries to get the previously saved timestamp from FILENAME, but if
it can't read the file returns 0. */
time_t prev;
if (access(filename, R_OK) == 0) {
prev = load_previous_time(filename);
}
else {
prev = 0;
}
return prev;
}
static int
get_tty_number(void)
{ /* Gets the number of the current tty. It assumes that the number is
an integer and consists of everything after the last `/' of the
tty's name. */
char *tty = get_tty_name();
char *num = strrchr(tty, '/') + 1;
return atoi(num);
}
static char
get_tty_type(void)
{ /* Gets the type of the tty represented by the first letter of the
type, either `t' or `p'. Assumes that the type comes immediately
after `/dev/'. */
char *tty = get_tty_name();
strtok(tty, "/"); /* dev */
return strtok(NULL, "/")[0];
}
static int
save_current_time(char *filename)
{ /* Save the timestamp for this moment to FILENAME. Returns `1' when
succesful, `0' when the file couldn't be opened. */
FILE *timefile = fopen(filename, "w");
time_t now;
if (!timefile)
return 0;
time(&now);
fprintf(timefile, "%ld", now);
fclose(timefile);
return 1;
}
static void
print_time_since(time_t lasttime)
{ /* Print the hours, minutes and seconds that have passed since
LASTTIME to `stdout'. */
double h, m, s;
time_t now;
time(&now);
s = difftime(now, lasttime);
if (s >= 60.0) {
m = floor(s / 60.0);
s -= m * 60;
if (m >= 60.0) {
h = floor(m / 60.0);
m -= h * 60;
printf("%.0lfh", h);
}
printf("%.0lfm", m);
}
printf("%.0lfs", s);
}
int
main()
{ /* This program prints a single letter represetation of the type and
number of the current tty and the time elapsed since the last
call to this program on this tty, or `new'. It then saves a
timestamp to a file in /tmp/ so that it can check the elapsed
time during its next run. */
char *filename = get_filename();
time_t lasttime = get_previous_time(filename);
printf("%c%d:", get_tty_type(), get_tty_number());
if (lasttime > 0) {
print_time_since(lasttime);
}
else {
puts("new");
}
save_current_time(filename);
free(filename);
return EXIT_SUCCESS;
}
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