psroute(1)

psroute/Makefile

@@ -0,0 +1,3 @@
+CFLAGS += -I../libpsargs
+
+psroute: psroute.o ../libpsargs/libpsargs.o

psroute/psroute.1

@@ -0,0 +1,44 @@
+.TH PSROUTE 1
+
+.SH NAME
+
+psroute \(en pipe standard output and standard error, independently
+
+.SH SYNOPSIS
+
+psroute
+"["
+.RB [ command
+.RB ( argument... )]
+"]"
+"["
+.RB [ command
+.RB ( argument... )]
+"]"
+"["
+.RB [ command
+.RB ( argument... )]
+"]"
+
+.SH DESCRIPTION
+
+Psroute runs the first given command, piping its standard output to the
+standard input of the second given command, and piping the first command's
+standard error to the standard input of the third given command.
+.PP
+Psroute's standard input is piped to the first given command. The second and
+third commands' standard output and error stream out of psroute normally.
+
+.SH DIAGNOSTICS
+
+Psroute will print an error message and exit with the appropriate status from
+sysexits(3) in the event of improper invocation or operating system error.
+Psroute will exit with the status of the first given command.
+
+.SH BUGS
+
+See psrelay(1).
+
+.SH COPYRIGHT
+
+Public domain.

psroute/psroute.c

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+#include <stdio.h> /* fprintf(3), perror(3), stderr */
+#if !defined EX_OSERR || !defined EX_USAGE
+#	include <sysexits.h>
+#endif
+#include <unistd.h> /* dup2(2), fork(2), pipe(2), STDERR_FILENO,
+                     * STDOUT_FILENO */
+#include <sys/types.h> /* <sys/wait.h> */
+#include <sys/wait.h> /* waitpid(2), WEXITSTATUS */
+#include "libpsargs.h" /* check_arg(3), corresponding_arg(3) */
+
+int oserr(char *s){
+
+	perror(s);
+
+	return EX_OSERR;
+}
+int main(int argc, char *argv[]){
+	int child;
+	char **corr;
+	char **curr;
+	int e[2];
+	int efd;
+	int i;
+	int o[2];
+	int ofd;
+	int pid;
+
+	if(argc < 2 || check_arg(curr = &argv[1]) != 3){
+		fprintf(stderr,
+			"Usage: %s \"[\" [command] (arguments...) \"]\""
+			"\t"	"\"[\" [command] (arguments...) \"]\""
+			" \"[\" [command (arguments...) \"]\"\n",
+			argc == 0 ? "<no argv[0]>" : argv[0]);
+		return EX_USAGE;
+	}
+
+	if(		(ofd = dup(STDOUT_FILENO)) < 0 /* preserve stdout */
+			|| (efd = dup(STDERR_FILENO)) < 0 /* and stderr */
+			|| pipe(o) < 0 /* establish out pipe */
+			|| pipe(e) < 0 /* and err pipe, and use them: */
+			|| dup2(o[1], STDOUT_FILENO) != STDOUT_FILENO
+			|| dup2(e[1], STDERR_FILENO) != STDERR_FILENO)
+		return oserr(argv[0]);
+
+	/* start the source command first because it's the most critical point
+	 * of failure */
+	*(corr = corresponding_arg(curr++)) = NULL;
+	switch(pid = fork()){
+		case  0:	execvp(curr[0], curr);
+		case -1:	return oserr(argv[0]);
+	}
+
+	/* restore preserved stdout/stderr */
+	if(		dup2(ofd, STDOUT_FILENO) != STDOUT_FILENO
+			|| dup2(efd, STDERR_FILENO) != STDERR_FILENO)
+		return oserr(argv[0]);
+
+	for(i = 1; i <= 2; ++i){
+		curr = corr + 1;
+		*(corr = corresponding_arg(curr++)) = NULL;
+		if(dup2(((i == 1) ? o : e)[0], STDIN_FILENO != STDIN_FILENO))
+			return oserr(argv[0]);
+		switch(fork()){
+		case  0:	execvp(curr[0], curr);
+		case -1:	return oserr(argv[0]);
+ 		}
+	}
+
+	waitpid(pid, &child, 0);
+
+	return WEXITSTATUS(child);
+}