independ pscat(1)

pscat/Makefile

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+all: pscat
+
+clean:
+	rm -rf ../dist/pscat ../dist/pscat.tar ../dist/pscat.tar.gz pscat
+
+dist: ../dist/pscat.tar.gz
+
+sane: pscat.c ../include/sysexits.h
+	$(CC) -DUSE_ASCII_H -DDONT_USE_SYSTEM_SYSEXITS -o pscat pscat.c
+
+pscat: pscat.c
+	$(CC) -o pscat pscat.c
+
+../dist/pscat: pscat
+	mkdir -p ../dist/pscat.tmp/bin/ ../dist/pscat.tmp/share/man/man1/
+	cp pscat ../dist/pscat.tmp/bin/pscat
+	cp pscat.1 ../dist/pscat.tmp/share/man/man1/pscat.1
+	mv ../dist/pscat.tmp ../dist/pscat
+
+../dist/pscat.tar: ../dist/pscat
+	cd ../dist/pscat && pax -w -x ustar . >../pscat.tar.tmp
+	mv ../dist/pscat.tar.tmp ../dist/pscat.tar
+
+../dist/pscat.tar.gz: ../dist/pscat.tar
+	gzip -c <../dist/pscat.tar >../dist/pscat.tar.gz.tmp
+	mv ../dist/pscat.tar.gz.tmp ../dist/pscat.tar.gz
+
+.PHONY: all clean sane

pscat/pscat.1

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+.TH PSCAT 1
+
+.SH NAME
+
+pscat \- concatenate the output of processes
+
+.SH SYNOPSIS
+
+pscat
+"[" 
+.RB [ utility
+.RB [ argument... ]]
+"]" ...
+
+.SH DESCRIPTION
+
+Pscat executes multiple commands, one after the other.
+This allows multiple processes to be piped as one to another program.
+
+.SH DIAGNOSTICS
+
+Pscat will print an error message and exit with the appropriate status from sysexits(3) if executed improperly.
+Pscat will exit with the sum of the child processes' exit statuses if run correctly.
+
+.SH BUGS
+
+Pscat's exit status isn't useful when run correctly; there's no way to tell which process failed if one did.
+This issue of ergonomics isn't obviously mendable as processes' standard outputs and standard errors are meant to both be conveyed.
+If either could be ignored the individual exit statuses could simply be printed.
+.PP
+Pscat's function is redundant to the sh(1) construct
+.RB { utility ; utility ;}
+- this is a feature, not a bug.
+
+.SH COPYRIGHT
+
+Public domain.

pscat/pscat.c

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+#ifndef DONT_USE_SYSTEM_SYSEXITS
+#	include <sysexits.h>
+#else
+#	include "../include/sysexits.h"
+#endif /* ifndef DONT_USE_SYSTEM_SYSEXITS */
+
+#include <stdio.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static char *program_name = "pscat";
+
+/* Originally designed to use parentheses but changed to brackets to escape the
+ * hassle of escaping them from the Bourne shell. */
+#ifndef USE_ASCII_H
+#	define L_PAREN '['
+#	define R_PAREN ']'
+#else
+#	include "../include/ascii.h"
+#	define L_PAREN ASCII_LEFT_SQUARE_BRACKET
+#	define R_PAREN ASCII_RIGHT_SQUARE_BRACKET
+#endif /* ifndef USE_ASCII_H */
+
+/* Test string containing { c, '\0' } without iteration.
+ * Theoretically saves a little bit of time compared to strcmp(3). */
+int
+scmpflat(char *s, int c){
+	return
+		s[0] != '\0'
+		&& s[1] == '\0'
+		&& s[0] == c
+	;
+}
+
+/* Verifies arguments to pscat are sensible. */
+int
+check_arg(char **argv){
+	enum {
+		UNINITIALIZED = 0,
+		NORMAL = 1,
+		INLPAREN = 2
+	} s;
+	int terms;
+
+	for(s = UNINITIALIZED, terms = 0; *argv != NULL; ++argv)
+		switch(s){
+		case UNINITIALIZED: case NORMAL:
+			if(scmpflat(*argv, L_PAREN))
+				s = INLPAREN;
+			else
+				return 0; /* syntax error */
+			break;
+		default: /* >= INLPAREN */
+			if(scmpflat(*argv, R_PAREN)){
+				--s;
+				terms += s == NORMAL;
+			}else if(scmpflat(*argv, L_PAREN)) /* ineligant */
+				++s;
+			break;
+		}
+
+	return terms;
+}
+
+int main(int argc, char *argv[]){
+	char **psstart;
+	int child;
+	int i;
+	int p;
+	int retval;
+	int terms;
+
+	retval = 0;
+
+	if((terms = check_arg(++argv)) == 0){
+		fprintf(stderr,
+			"Usage: %s \"[\" [utility [argument...]] \"]\" ...\n",
+			argv[0] == NULL ? program_name : argv[0]
+		);
+		return EX_USAGE;
+	}
+
+	/* loop starts with *argv -> the next L_PAREN */
+	for(i = 0; i < terms; ++i){
+		psstart = ++argv;
+		p = 1;
+		while(p > 0){
+			++argv;
+			/* branching here potentially saves a comparison.
+			 * this seems like the most optimal way to do this,
+			 * maybe it isn't, i don't care too much */
+			if(scmpflat(*argv, L_PAREN))
+				++p;
+			else if(scmpflat(*argv, R_PAREN))
+				--p;
+		}
+		/* *argv -> the corresponding R_PAREN. turn it into NULL to
+		 * terminate the argument list to send to execvp(3) */
+		*argv = NULL;
+		if(fork() == 0){
+			execvp(psstart[0], psstart);
+		}else
+			wait(&child);
+		/* interpret status information from wait(2) */
+		if(WIFEXITED(child))
+			retval += WEXITSTATUS(child);
+		++argv;
+	}
+
+	return retval;
+}