Source code of cal in UNIX

[oakdeveloper]

Hi,

I am learning Java and wish to develop a console based calendar application in Java similar to the lines of the 'cal' command in UNIX. I have learnt that UNIX was re-written in C language. Is there a way I could get the source code for the 'cal' application so that I could implement a similar one in Java ?

Thanks,
Babu

[mali2297]

The program cal is included in the debian package bsdutils. Try fetching the source with the command


apt-get source bsdutils

[Paul Miller]

Is there a way I could get the source code for the 'cal' application so that I could implement a similar one in Java ?


From UNIX v7:



char dayw[] = {
" S M Tu W Th F S"
};
char *smon[]= {
"January", "February", "March", "April",
"May", "June", "July", "August",
"September", "October", "November", "December",
};
char string[432];
main(argc, argv)
char *argv[];
{
register y, i, j;
int m;

if(argc < 2) {
printf("usage: cal [month] year\n");
exit(0);
}
if(argc == 2)
goto xlong;

/*
* print out just month
*/

m = number(argv[1]);
if(m<1 || m>12)
goto badarg;
y = number(argv[2]);
if(y<1 || y>9999)
goto badarg;
printf(" %s %u\n", smon[m-1], y);
printf("%s\n", dayw);
cal(m, y, string, 24);
for(i=0; i<6*24; i+=24)
pstr(string+i, 24);
exit(0);

/*
* print out complete year
*/

xlong:
y = number(argv[1]);
if(y<1 || y>9999)
goto badarg;
printf("\n\n\n");
printf(" %u\n", y);
printf("\n");
for(i=0; i<12; i+=3) {
for(j=0; j<6*72; j++)
string[j] = '\0';
printf(" %.3s", smon[i]);
printf(" %.3s", smon[i+1]);
printf(" %.3s\n", smon[i+2]);
printf("%s %s %s\n", dayw, dayw, dayw);
cal(i+1, y, string, 72);
cal(i+2, y, string+23, 72);
cal(i+3, y, string+46, 72);
for(j=0; j<6*72; j+=72)
pstr(string+j, 72);
}
printf("\n\n\n");
exit(0);

badarg:
printf("Bad argument\n");
}

number(str)
char *str;
{
register n, c;
register char *s;

n = 0;
s = str;
while(c = *s++) {
if(c<'0' || c>'9')
return(0);
n = n*10 + c-'0';
}
return(n);
}

pstr(str, n)
char *str;
{
register i;
register char *s;

s = str;
i = n;
while(i--)
if(*s++ == '\0')
s[-1] = ' ';
i = n+1;
while(i--)
if(*--s != ' ')
break;
s[1] = '\0';
printf("%s\n", str);
}

char mon[] = {
0,
31, 29, 31, 30,
31, 30, 31, 31,
30, 31, 30, 31,
};

cal(m, y, p, w)
char *p;
{
register d, i;
register char *s;

s = p;
d = jan1(y);
mon[2] = 29;
mon[9] = 30;

switch((jan1(y+1)+7-d)%7) {

/*
* non-leap year
*/
case 1:
mon[2] = 28;
break;

/*
* 1752
*/
default:
mon[9] = 19;
break;

/*
* leap year
*/
case 2:
;
}
for(i=1; i<m; i++)
d += mon[i];
d %= 7;
s += 3*d;
for(i=1; i<=mon[m]; i++) {
if(i==3 && mon[m]==19) {
i += 11;
mon[m] += 11;
}
if(i > 9)
*s = i/10+'0';
s++;
*s++ = i%10+'0';
s++;
if(++d == 7) {
d = 0;
s = p+w;
p = s;
}
}
}

/*
* return day of the week
* of jan 1 of given year
*/

jan1(yr)
{
register y, d;

/*
* normal gregorian calendar
* one extra day per four years
*/

y = yr;
d = 4+y+(y+3)/4;

/*
* julian calendar
* regular gregorian
* less three days per 400
*/

if(y > 1800) {
d -= (y-1701)/100;
d += (y-1601)/400;
}

/*
* great calendar changeover instant
*/

if(y > 1752)
d += 3;

return(d%7);
}

[lisati]

From UNIX v7:


A rewrite to get rid of the "goto" is left as an exercise for the reader......

[oakdeveloper]

Thanks to all!

[nvteighen]

Er... wait, UNIX is not Free Software. Posting UNIX source code here may be copyright infringement!

Why not just look at GNU cal?

[JordyD]

A rewrite to get rid of the "goto" is left as an exercise for the reader......

Plus conversion from old C to ANSI C.

[rjack]

Another version (http://git.kernel.org/?p=utils/util-linux-ng/util-linux-ng.git;a=blob;f=misc-utils/cal.c;h=a8534b8ca9e890ea9cc048fb987b0e0503ed045d;h b=e2de50f8b4da55675dc1444c101f402e798a8593) from the util-linux-ng git repository.