parse_time - Man Page

parse and unparse time intervals


The roken library (libroken, -lroken)


#include <parse_time.h>

parse_time(const char *timespec, const char *def_unit);

print_time_table(FILE *f);

unparse_time(int seconds, char *buf, size_t len);

unparse_time_approx(int seconds, char *buf, size_t len);


The parse_time() function converts the period of time specified into a number of seconds. The timespec can be any number of ⟨number unit⟩ pairs separated by comma and whitespace. The number can be negative. Numbers without explicit units are taken as being def_unit.

The unparse_time() and unparse_time_approx() do the opposite of parse_time(), that is they take a number of seconds and express that as human readable strings. unparse_time produces an exact time, while unparse_time_approx restricts the result to include only one unit.

print_time_table() prints a descriptive list of available units on the passed file descriptor.

The possible units include:

second, s
minute, m
hour, h

seven days


30 days


365 days

Units names can be arbitrarily abbreviated (as long as they are unique).

Return Values

parse_time() returns the number of seconds that represents the expression in timespec or -1 on error. unparse_time() and unparse_time_approx() return the number of characters written to buf. if the return value is greater than or equal to the len argument, the string was too short and some of the printed characters were discarded.


#include <stdio.h>
#include <parse_time.h>

main(int argc, char **argv)
    int i;
    int result;
    char buf[128];
    for (i = 1; i < argc; i++) {
	result = parse_time(argv[i], "second");
	if(result == -1) {
	    fprintf(stderr, "%s: parse error\n", argv[i]);
	printf("parse_time = %d\n", result);
	unparse_time(result, buf, sizeof(buf));
	printf("unparse_time = %s\n", buf);
	unparse_time_approx(result, buf, sizeof(buf));
	printf("unparse_time_approx = %s\n", buf);
    return 0;
$ ./a.out "1 minute 30 seconds" "90 s" "1 y -1 s"
1   year = 365 days
1  month = 30 days
1   week = 7 days
1    day = 24 hours
1   hour = 60 minutes
1 minute = 60 seconds
1 second
parse_time = 90
unparse_time = 1 minute 30 seconds
unparse_time_approx = 1 minute
parse_time = 90
unparse_time = 1 minute 30 seconds
unparse_time_approx = 1 minute
parse_time = 31535999
unparse_time = 12 months 4 days 23 hours 59 minutes 59 seconds
unparse_time_approx = 12 months


Since parse_time() returns -1 on error there is no way to parse "minus one second". Currently "s" at the end of units is ignored. This is a hack for English plural forms. If these functions are ever localised, this scheme will have to change.

Referenced By

The man pages print_time_table(3), unparse_time(3) and unparse_time_approx(3) are aliases of parse_time(3).

November 17, 2013