psrelay(1)
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psrelay/Makefile
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psrelay/Makefile
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CFLAGS += -I../libpsargs
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psrelay: psrelay.o ../libpsargs/libpsargs.o
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psrelay/psrelay.1
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psrelay/psrelay.1
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.TH PSRELAY 1
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.SH NAME
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psrelay \(en conditionally execute a process
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.SH SYNOPSIS
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psrelay
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"["
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.RB [ command
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.RB ( argument... )]
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"]"
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"["
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.RB [ command
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.RB ( argument... )]
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"]"
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.SH DESCRIPTION
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Psrelay runs the first given command and, if it exits successfully, runs the
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second given command, exiting with the status of the second command.
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.PP
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Standard input given to psrelay is not directed to the first given command,
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only to the second given command.
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.SH DIAGNOSTICS
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Psrelay will print an error message and exit with the appropriate status from
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sysexits(3) in the event of improper invocation or operating system error.
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Psrelay will exit with the status of the second given command if run without
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error.
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.SH BUGS
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Unintuitively, "psrelay [ wc -c <file | xargs test 4 = ] [ cat ]" will
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redirect the contents of "file" into "psrelay [ wc -c" and pipe that output to
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"xargs test 4 = ] [ cat ]".
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.SH COPYRIGHT
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Public domain.
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55
psrelay/psrelay.c
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psrelay/psrelay.c
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#include <errno.h> /* errno */
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#include <stdio.h> /* fprintf(3) */
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#include <string.h> /* strerror(3) */
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#if !defined EX_OK || !defined EX_OSERR || !defined EX_USAGE
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# include <sysexits.h>
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#endif
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#include <unistd.h> /* fork(2) */
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#include <sys/types.h> /* <sys/wait.h> */
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#include <sys/wait.h> /* wait(2), WIFEXITED, WEXITSTATUS */
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#include "libpsargs.h"
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int oserr(char *argv0, char *s){
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fprintf(stderr, "%s: %s\n", argv0, s);
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return EX_OSERR;
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}
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int usage(char *s){
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fprintf(stderr,
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"Usage: %s \"[\" [command (arguments...)] \"]\""
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" \"[\" [command (arguments...)] \"]\"\n",
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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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int child;
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char **corr;
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char **curr;
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int i;
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int r;
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if(argc < 2 || check_arg(curr = &argv[1]) != 2)
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return usage(argc == 0 ? "<no argv[0]>" : argv[0]);
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do{
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*(corr = corresponding_arg(curr++)) = NULL;
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if(i == 1 || (r = fork()) == 0)
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execvp(*curr, curr);
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if(i == 1 || r == -1 || r == 0)
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return oserr(argv[0], strerror(errno));
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wait(&child);
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if(!WIFEXITED(child) || WEXITSTATUS(child) != 0)
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return 1;
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curr = corr + 1;
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}while(++i < 2);
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/* UNREACHABLE */
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}
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