16 Feb
2023
16 Feb
'23
2:24 p.m.
Here is a simplified 'more' command for Unix V7:
/*********************************************************************
* UNIX pager (v7 compatible) Chipmaster and KenUnix
*
* cc -o more more.c
*
* Usage examples:
* man wall | more
* more xyz
* more abc def xyz
*
* Started February 15th, 2023 YeOlPiShack.net
*
* This is the ultimately dumbest version of more I have experienced.
* Its main purpose is to illustrate the use of /dev/tty to interact
* with the user while in a filter role (stdin -> stdout). This also
* leaves stderr clear for actual errors.
*
*
* NOTES on Antiquity:
*
* - The early C syntax didn't allow for combining type information
* in the parenthesized argument list only the names were listed.
* Then a "variable" list followed the () and preceded the { that
* declared the types for the argument list.
*
* - There is no "void", specifically there is no distinction
* between a function that returns an int or nothing at all.
*
* - Many of the modern day header files aren't there.
*
* - Apparently "/dev/tty" couldn't be opened for both reading and
* writing on the same FD... at least not in our VM.
*
* - Apparently \a wasn't defined yet either. So I use the raw code
* \007.
*
* - Modern compilers gripe if you do an assignment and comparison in
* the same statement without enclosing the assignment in (). The
* original compilers did not. So if it looks like there are too
* many ()s it's to appease the modern compiler gods.
*
* - I'm not sure where they hid errno if there was one. I'd think
* there had to be. Maybe Kernighan or Pike knows...
*
*********************************************************************/
#include <stdio.h>
/*** Let's make some assumptions about our terminal columns and lines. ***/
#define T_COLS 80
#define T_LINES 24
/*** Let's set up our global working environment ***/
FILE *cin; /* TTY (in) */
FILE *cout; /* | (out) */
int ct = 0;
/*** message to stderr and exit with failure code ***/
err(msg)
char *msg;
{
fputs(msg, stderr);
exit(1);
}
/*** A poor man's CLear Screen ***
*
* Yup! This is how they used to do it, so says THE Kenrighan & Pike!
* termcap?!?! What's that?
*/
cls()
{
int x;
for(x=0; x<T_LINES; ++x) fputc('\n', cout);
ct = 0; /* reset global line count */
}
/*** The PAUSE prompt & wait ***/
pause()
{
char in[T_COLS+1]; /* TTY input buffer */
fflush(stdout); /*JIC*/
fputs("--- [ENTER] to continue --- Ctrl-d exits ", cout);
fflush(cout);
if(!fgets(in, 81, cin)) {
/* ^D / EOF */
fputc('\n', cout); /* cleaner terminal */
exit(0);
}
}
/*** Read and page a "file" ***/
int pg(f)
FILE *f;
{
char buf[T_COLS+1]; /* input line: usual term width + \0 */
/*** read and page stdin ***/
while(fgets(buf, sizeof(buf), f)) {
/* page break at T_LINES */
if(++ct==T_LINES) {
pause();
ct = 1;
}
fputs(buf, stdout);
}
return 0;
}
/*** Let's do some paging!! ***/
int main(argc, argv)
int argc;
char *argv[];
{
FILE *in;
int x, er;
/*** Grab a direct line to the TTY ***/
if(!(cin=fopen("/dev/tty", "r")) ||
!(cout=fopen("/dev/tty", "w")))
err("\007Couldn't get controlling TTY\n");
/*** with CLI args ***/
if(argc>1) {
er = 0;
for(x=1; x<argc; ++x) {
if(argc>2) {
if(!er) cls();
er = 0;
/* remember all user interaction is on /dev/tty (cin/cout) */
fprintf(cout, ">>> %s <<<\n", argv[x]);
pause();
}
/* - is tradition for stdin */
if(strcmp("-", argv[x])==0) {
pg(stdin);
/* it must be a file! */
} else if((in=fopen(argv[x], "r"))) {
pg(in);
fclose(in);
} else {
/* errors go on stderr... JIC someone want to log */
fprintf(stderr, "Could not open '%s'!\n", argv[x]);
fflush(stderr);
er = 1; /* this prevents cls() above. */
}
}
/*** no args - read and page stdin ***/
} else {
pg(stdin);
}
return 0;
}
End...
--
WWL 📚