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pg(1): add -p option

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This commit is contained in:
dtb 2024-04-22 07:52:41 -06:00
parent 68919bf877
commit 9c1e0d785d
Signed by: trinity
GPG Key ID: 31FF85CCB6DC7641
2 changed files with 84 additions and 38 deletions
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13
docs/pg.1
View File

@ -9,10 +9,23 @@
pg \(en paginate
.SH SYNOPSIS
pg
.RB ( -p
.RB [ prompt ])
.SH DESCRIPTION
Pg prints standard input to standard output, accepting commands between pages.
.SH OPTIONS
.B -p
.RS
Replaces the default prompt (": ") with the next argument.
.RE
.SH DIAGNOSTICS
Pg returns an unsuccessful exit code if the tty couldn't be opened or if pg was

109
src/pg.c
View File

@ -22,11 +22,14 @@
* NULL */
#include <stdlib.h> /* size_t */
#include <string.h> /* strchr(3), strcmp(3), strerror(3), strtok(3) */
#include <unistd.h> /* getopt(3) */
#if !defined EX_OK || !defined EX_SOFTWARE || !defined EX_USAGE
# include <sysexits.h>
#endif
#define CMDLINE_MAX 99+1 /* Maximum length of command line. */
/* Done while looking at plan9ports' src/cmd/p.c.
* Taken from plan9 are the interface (minus p(1)'s shell escaping and the
* ability to page multiple files) and the practice of reading /dev/tty to get
@ -46,48 +49,64 @@ static char *program_name = "pg";
/* Commands start with cmd_. They take an argc and NULL-terminated argv, like
* main, and return one of the following RET_ enums as a status. */
enum{ RET_ARGSERROR, RET_OK, RET_NOCMD, RET_REQSHUTDOWN, RET_SOFTWARE };
enum{ RET_OK, RET_REQSHUTDOWN, RET_USAGE, RET_NOCMD, RET_SOFTWARE };
static int page_bytes(FILE *f, size_t l){
/* Page at most l bytes from f without consideration of a buffer (print them to
* stdout). */
static int pg_b_u(FILE *f, size_t l){
int c;
while((c = fgetc(f)) != EOF)
if((c = fputc(c, stdout)) == EOF || --l == 0)
break;
return c == EOF
? RET_REQSHUTDOWN
: RET_OK;
return c;
}
static int page_lines(FILE *f, size_t l){
/* Page at most l lines, which are lengths of characters terminated by nl, from
* f without consideration of a buffer (print them to stdout). */
static int pg_l_u(FILE *f, size_t l, char nl){
int c;
while((c = fgetc(f)) != EOF)
if((c = fputc(c, stdout)) == EOF || (l -= (c == '\n')) == 0)
if((c = fputc(c, stdout)) == EOF || (l -= (c == nl)) == 0)
break;
return c == EOF
? RET_REQSHUTDOWN
: RET_OK;
return c;
}
static int cmd_quit(int argc, char **argv){ return RET_REQSHUTDOWN; }
static int cmd_default_page(int argc, char **argv){
if(strtok(NULL, whitespace) != NULL)
return RET_ARGSERROR; /* This shouldn't be possible. */
if(argc > 1) /* This shouldn't be possible. */
return RET_USAGE;
if(default_page_unit.type == BYTES)
return page_bytes(input, default_page_unit.quantity);
return pg_b_u(input, default_page_unit.quantity) == EOF
? RET_REQSHUTDOWN
: RET_OK;
else if(default_page_unit.type == LINES)
return page_lines(input, default_page_unit.quantity);
return pg_l_u(input, default_page_unit.quantity, '\n') == EOF
? RET_REQSHUTDOWN
: RET_OK;
else
return RET_SOFTWARE;
}
static int cmd_page_down_lines(int argc, char **argv){
switch(argc){
case 1:
return cmd_default_page(argc, argv);
case 2: /* not implemented */
default:
fprintf(stderr, "Usage: %s" /*" (lines)"*/ "\n", argv[0]);
return RET_USAGE;
}
}
/* A CmdMap must be NULL-terminated. */
static struct CmdMap{ char *name; int (*fn)(int, char **); } cmd_map[] = {
{ "", cmd_default_page },
{ "+", cmd_page_down_lines },
/* don't make the user feel trapped */
{ "exit", cmd_quit }, { "q", cmd_quit }, { ":q", cmd_quit },
@ -100,6 +119,9 @@ static struct CmdMap{ char *name; int (*fn)(int, char **); } cmd_map[] = {
/* Find and execute the command in the command map, given a corresponding
* command line. */
static int cmdline_exec(struct CmdMap *map, char *cmdline){
/* Command line word splitting is naive and based on whitespace ONLY; no
* fancy quoting or escaping here. Adding that would (ideally) entail
* replacing strtok(3) with something specific to this task. */
static int argc;
static char *argv[ARGV_MAX];
@ -109,7 +131,7 @@ static int cmdline_exec(struct CmdMap *map, char *cmdline){
argv[argc] = cmdline;
argv[++argc] = NULL;
}else{
while((argv[++argc] = strtok(NULL , whitespace)) != NULL
while((argv[++argc] = strtok(NULL, whitespace)) != NULL
&& argc < ARGV_MAX);
}
@ -121,49 +143,60 @@ static int cmdline_exec(struct CmdMap *map, char *cmdline){
return RET_NOCMD;
}
int usage(char *s){
fprintf(stderr, "Usage: %s (-p [prompt])\n", s);
return EX_USAGE;
}
int main(int argc, char *argv[]){
unsigned char cmd[99+1];
int r;
unsigned char cmd[CMDLINE_MAX];
FILE *t;
input = stdin;
if(argc > 0)
if(argc < 1)
program_name = argv[0];
else{
int c;
if(argc > 1){
fprintf(stderr, "Usage: %s\n", program_name);
return EX_USAGE;
while((c = getopt(argc, argv, "p:")) != -1)
switch(c){
case 'p': prompt = optarg; break;
default:
return usage(program_name);
}
}
if(argc > optind)
return usage(program_name);
if((t = fopen("/dev/tty", "rb")) == NULL){
fprintf(stderr, "%s: /dev/tty: %s\n", program_name, strerror(errno));
return EX_SOFTWARE;
}
r = 0;
for(;;){
if(r != RET_REQSHUTDOWN){
fputs(prompt, stderr);
fgets((char *)cmd, (sizeof cmd) / (sizeof *cmd), t);
if(strchr((char *)cmd, '\n') == NULL){ /* fast-forward stream */
int c;
fputs(prompt, stderr);
fgets((char *)cmd, (sizeof cmd) / (sizeof *cmd), t);
if(strchr((char *)cmd, '\n') == NULL){ /* fast-forward stream */
int c;
while((c = fgetc(t)) != '\n')
if(c == EOF)
break;
}
while((c = fgetc(t)) != '\n')
if(c == EOF)
break;
}
if(r == RET_REQSHUTDOWN || feof(t)){
fclose(t);
if(feof(t))
return EX_OK;
}
switch((r = cmdline_exec(cmd_map, (char *)cmd))){
case RET_ARGSERROR: case RET_NOCMD: case RET_OK:
switch(cmdline_exec(cmd_map, (char *)cmd)){
case RET_USAGE: case RET_NOCMD: case RET_OK:
break;
case RET_REQSHUTDOWN: case RET_SOFTWARE: default:
r = RET_REQSHUTDOWN;
case RET_SOFTWARE:
return EX_SOFTWARE;
case RET_REQSHUTDOWN: default:
return EX_OK;
}
}