retry.c

/*
 ============================================================================
 Name        : retry.c
 Author      : Heikki Pernu
 Version     :
 Copyright   :
 Description : Retry ptog in C, Ansi-style
 ============================================================================
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <getopt.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>

#include "version.h"

void usage() {
	fprintf(stderr,
			"%s [--version] [-hv] [-t timeout] times delay cmd [cmdarg] [cmdarg] [...]\n",
			"retry");
	exit(EXIT_FAILURE);
}

/**
 * Convert a time in arg string to seconds in integer
 */
int totime(char *arg) {
	if (strlen(arg) > 0) {
		int number = atoi(arg);

		switch (*(arg + strlen(arg) - 1)) {
		case 'h': // Hours
			return number * 60 * 60;
		case 'm': // Minutes
			return number * 60;
		default:
			return number;
		}
	}
	return 0;
}

extern char *optarg;
extern int optind;

int main(int argc, char * const argv[]) {
	int opt = 0;
	int verbosity = 0;
	int timeout = 0;
	int count = 0;
	int delay = 0;
	int expect = 0; // What value to expect

	if (argc>=2 && strcmp("--version",argv[1])==0) {
		fprintf(stderr,"%s\n",version);
		exit(0);
	}

	while ((opt = getopt(argc, argv, "+hvt:")) != -1) {
		switch (opt) {
		case 'h':
			usage();
			break;
		case 'v':
			verbosity++;
			break;
		case 't':
			timeout = totime(optarg);
			break;
		default:
			fprintf(stderr, "Unknown option %c\n", opt);
			usage();
			break;
		}
	}
	argv += optind;
	argc -= optind;

	if (argc < 3) {
		fprintf(stderr, "At least three arguments expected\n");
		usage();
		/* NOT REACHED */
	}
	count = totime(argv[0]);
	argv++;
	delay = totime(argv[0]);
	argv++;

	// Do fork, run the actual command in the background, possibly with timeout
	pid_t pid = 0;
	int status;
	FILE *out = NULL;
	FILE *err = NULL;

	do {
		if (out != NULL)
			fclose(out);
		if (err != NULL)
			fclose(err);
		if ((out = tmpfile()) == NULL) {
			perror("Unable to create temp file for stdout buffer");
			exit(-1);
		}
		if ((err = tmpfile()) == NULL) {
			perror("Unable to create temp file for stderr buffer");
			exit(-1);
		}

		if ((pid = fork()) == 0) {
			/* CHILD
			 * Run the actual program */
			// Should not go outside of execvp
			alarm(timeout); // Timeout with signal if timeout reached
			if (dup2(fileno(out), STDOUT_FILENO) == -1) {
				perror("Unable to redirecto stdout in subprocess");
				exit(-1);
			}
			fclose(out);
			if (dup2(fileno(err), STDERR_FILENO) == -1) {
				perror("Unable to redirecto stderr in subprocess");
				exit(-1);
			}
			fclose(err);
			exit(execvp(argv[0], argv));
		}
		/* PARENT
		 * Wait for child termination */
		wait(&status);
		if (WEXITSTATUS(status) != expect)
			sleep(delay);
	} while (--count > 0 && WEXITSTATUS(status) != expect);
	fflush(out);
	fflush(err);
	struct stat st;

	// Copy saved stdout from subprocess to real stdout
	if (fstat(fileno(out), &st) != 0) {
		perror("Unable to check the stdout of subprocess");
		exit(-1);
	} else if (st.st_size > 0) {
		char buf[4096];
		size_t n;
		fseek(out, 0, SEEK_SET);
		while (!feof(out)) {
			n = fread(buf, 1, sizeof(buf), out);
			fwrite(buf, 1, n, stdout);
		}
	}
	fflush(stdout);

	// Copy saved stderr from subprocess to real stderr
	if (fstat(fileno(err), &st) != 0) {
		perror("Unable to check the stdout of subprocess");
		exit(-1);
	} else if (st.st_size > 0) {
		char buf[4096];
		size_t n;
		fseek(err, 0, SEEK_SET);
		while (!feof(err)) {
			n = fread(buf, 1, sizeof(buf), err);
			fwrite(buf, 1, n, stderr);
		}
	}
	fflush(stderr);

	return WEXITSTATUS(status);
}