WIP: scroll(1) #127
13
docs/pg.1
13
docs/pg.1
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@ -9,10 +9,23 @@
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pg \(en paginate
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.SH SYNOPSIS
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pg
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.RB ( -p
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.RB [ prompt ])
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.SH DESCRIPTION
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Pg prints standard input to standard output, accepting commands between pages.
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.SH OPTIONS
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.B -p
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.RS
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Replaces the default prompt (": ") with the next argument.
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.RE
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.SH DIAGNOSTICS
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Pg returns an unsuccessful exit code if the tty couldn't be opened or if pg was
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97
src/pg.c
97
src/pg.c
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@ -22,11 +22,14 @@
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* NULL */
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#include <stdlib.h> /* size_t */
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#include <string.h> /* strchr(3), strcmp(3), strerror(3), strtok(3) */
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#include <unistd.h> /* getopt(3) */
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#if !defined EX_OK || !defined EX_SOFTWARE || !defined EX_USAGE
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# include <sysexits.h>
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#endif
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#define CMDLINE_MAX 99+1 /* Maximum length of command line. */
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/* Done while looking at plan9ports' src/cmd/p.c.
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* Taken from plan9 are the interface (minus p(1)'s shell escaping and the
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* ability to page multiple files) and the practice of reading /dev/tty to get
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@ -46,48 +49,64 @@ static char *program_name = "pg";
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/* Commands start with cmd_. They take an argc and NULL-terminated argv, like
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* main, and return one of the following RET_ enums as a status. */
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enum{ RET_ARGSERROR, RET_OK, RET_NOCMD, RET_REQSHUTDOWN, RET_SOFTWARE };
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enum{ RET_OK, RET_REQSHUTDOWN, RET_USAGE, RET_NOCMD, RET_SOFTWARE };
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static int page_bytes(FILE *f, size_t l){
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/* Page at most l bytes from f without consideration of a buffer (print them to
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* stdout). */
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static int pg_b_u(FILE *f, size_t l){
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int c;
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while((c = fgetc(f)) != EOF)
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if((c = fputc(c, stdout)) == EOF || --l == 0)
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break;
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return c == EOF
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? RET_REQSHUTDOWN
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: RET_OK;
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return c;
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}
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static int page_lines(FILE *f, size_t l){
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/* Page at most l lines, which are lengths of characters terminated by nl, from
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* f without consideration of a buffer (print them to stdout). */
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static int pg_l_u(FILE *f, size_t l, char nl){
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int c;
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while((c = fgetc(f)) != EOF)
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if((c = fputc(c, stdout)) == EOF || (l -= (c == '\n')) == 0)
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if((c = fputc(c, stdout)) == EOF || (l -= (c == nl)) == 0)
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break;
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return c == EOF
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? RET_REQSHUTDOWN
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: RET_OK;
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return c;
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}
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static int cmd_quit(int argc, char **argv){ return RET_REQSHUTDOWN; }
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static int cmd_default_page(int argc, char **argv){
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if(strtok(NULL, whitespace) != NULL)
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return RET_ARGSERROR; /* This shouldn't be possible. */
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if(argc > 1) /* This shouldn't be possible. */
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return RET_USAGE;
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if(default_page_unit.type == BYTES)
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return page_bytes(input, default_page_unit.quantity);
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return pg_b_u(input, default_page_unit.quantity) == EOF
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? RET_REQSHUTDOWN
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: RET_OK;
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else if(default_page_unit.type == LINES)
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return page_lines(input, default_page_unit.quantity);
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return pg_l_u(input, default_page_unit.quantity, '\n') == EOF
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? RET_REQSHUTDOWN
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: RET_OK;
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else
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return RET_SOFTWARE;
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}
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static int cmd_page_down_lines(int argc, char **argv){
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switch(argc){
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case 1:
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return cmd_default_page(argc, argv);
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case 2: /* not implemented */
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default:
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fprintf(stderr, "Usage: %s" /*" (lines)"*/ "\n", argv[0]);
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return RET_USAGE;
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}
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}
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/* A CmdMap must be NULL-terminated. */
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static struct CmdMap{ char *name; int (*fn)(int, char **); } cmd_map[] = {
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{ "", cmd_default_page },
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{ "+", cmd_page_down_lines },
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/* don't make the user feel trapped */
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{ "exit", cmd_quit }, { "q", cmd_quit }, { ":q", cmd_quit },
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@ -100,6 +119,9 @@ static struct CmdMap{ char *name; int (*fn)(int, char **); } cmd_map[] = {
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/* Find and execute the command in the command map, given a corresponding
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* command line. */
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static int cmdline_exec(struct CmdMap *map, char *cmdline){
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/* Command line word splitting is naive and based on whitespace ONLY; no
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* fancy quoting or escaping here. Adding that would (ideally) entail
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* replacing strtok(3) with something specific to this task. */
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static int argc;
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static char *argv[ARGV_MAX];
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@ -109,7 +131,7 @@ static int cmdline_exec(struct CmdMap *map, char *cmdline){
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argv[argc] = cmdline;
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argv[++argc] = NULL;
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}else{
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while((argv[++argc] = strtok(NULL , whitespace)) != NULL
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while((argv[++argc] = strtok(NULL, whitespace)) != NULL
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&& argc < ARGV_MAX);
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}
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@ -121,29 +143,40 @@ static int cmdline_exec(struct CmdMap *map, char *cmdline){
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return RET_NOCMD;
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}
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int usage(char *s){
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fprintf(stderr, "Usage: %s (-p [prompt])\n", s);
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return EX_USAGE;
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}
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int main(int argc, char *argv[]){
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unsigned char cmd[99+1];
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int r;
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unsigned char cmd[CMDLINE_MAX];
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FILE *t;
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input = stdin;
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if(argc > 0)
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if(argc < 1)
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program_name = argv[0];
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else{
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int c;
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if(argc > 1){
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fprintf(stderr, "Usage: %s\n", program_name);
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return EX_USAGE;
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while((c = getopt(argc, argv, "p:")) != -1)
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switch(c){
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case 'p': prompt = optarg; break;
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default:
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return usage(program_name);
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}
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}
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if(argc > optind)
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return usage(program_name);
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if((t = fopen("/dev/tty", "rb")) == NULL){
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fprintf(stderr, "%s: /dev/tty: %s\n", program_name, strerror(errno));
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return EX_SOFTWARE;
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}
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r = 0;
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for(;;){
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if(r != RET_REQSHUTDOWN){
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fputs(prompt, stderr);
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fgets((char *)cmd, (sizeof cmd) / (sizeof *cmd), t);
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if(strchr((char *)cmd, '\n') == NULL){ /* fast-forward stream */
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@ -153,17 +186,17 @@ int main(int argc, char *argv[]){
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if(c == EOF)
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break;
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}
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}
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if(r == RET_REQSHUTDOWN || feof(t)){
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fclose(t);
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return EX_OK;
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}
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switch((r = cmdline_exec(cmd_map, (char *)cmd))){
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case RET_ARGSERROR: case RET_NOCMD: case RET_OK:
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if(feof(t))
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return EX_OK;
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switch(cmdline_exec(cmd_map, (char *)cmd)){
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case RET_USAGE: case RET_NOCMD: case RET_OK:
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break;
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case RET_REQSHUTDOWN: case RET_SOFTWARE: default:
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r = RET_REQSHUTDOWN;
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case RET_SOFTWARE:
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return EX_SOFTWARE;
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case RET_REQSHUTDOWN: default:
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return EX_OK;
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}
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}
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