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 📚