NAME

     parse_time, print_time_table, unparse_time, unparse_time_approx, — parse and unparse time
     intervals

LIBRARY

     The roken library (libroken, -lroken)

SYNOPSIS

     #include <parse_time.h>

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

     void
     print_time_table(FILE *f);

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

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

DESCRIPTION

     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
           day
           week   seven days
           month  30 days
           year   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.

EXAMPLES

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

     int
     main(int argc, char **argv)
     {
         int i;
         int result;
         char buf[128];
         print_time_table(stdout);
         for (i = 1; i < argc; i++) {
             result = parse_time(argv[i], "second");
             if(result == -1) {
                 fprintf(stderr, "%s: parse error\n", argv[i]);
                 continue;
             }
             printf("--\n");
             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

BUGS

     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.