A small I/O bound program to copy N bytes from an input file to an output file.

How to write a C Program : A small I/O bound program to copy N bytes from an input file to an output file. May read the input file multiple times if N is larger than the size of the input file in C Programming Language ?

/*
* Description: A small i/o bound program to copy N bytes from an input
* file to an output file. May read the input file multiple
* times if N is larger than the size of the input file.
*/
/* Include Flags */
#define _GNU_SOURCE
/* System Includes */
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sched.h>
/* Local Defines */
#define MAXFILENAMELENGTH 80
#define DEFAULT_INPUTFILENAME "rwinput"
#define DEFAULT_OUTPUTFILENAMEBASE "rwoutput"
#define DEFAULT_BLOCKSIZE 1024
#define DEFAULT_TRANSFERSIZE 1024*100
int main(int argc, char* argv[]){
int i;
int rv;
int inputFD;
int outputFD;
int numProcesses;
char inputFilename[MAXFILENAMELENGTH];
char outputFilename[MAXFILENAMELENGTH];
char outputFilenameBase[MAXFILENAMELENGTH];
struct sched_param param;
ssize_t transfersize = 0;
ssize_t blocksize = 0;
char* transferBuffer = NULL;
ssize_t buffersize;
int policy;
ssize_t bytesRead = 0;
ssize_t totalBytesRead = 0;
int totalReads = 0;
ssize_t bytesWritten = 0;
ssize_t totalBytesWritten = 0;
int totalWrites = 0;
int inputFileResets = 0;
pid_t id;
/* Process program arguments to select run-time parameters */
/* Set supplied transfer size or default if not supplied */
if(argc < 2){
transfersize = DEFAULT_TRANSFERSIZE;
}
else{
transfersize = atol(argv[1]);
if(transfersize < 1){
fprintf(stderr, "Bad transfersize value\n");
exit(EXIT_FAILURE);
}
}
/* Set supplied block size or default if not supplied */
if(argc < 3){
blocksize = DEFAULT_BLOCKSIZE;
}
else{
blocksize = atol(argv[2]);
if(blocksize < 1){
fprintf(stderr, "Bad blocksize value\n");
exit(EXIT_FAILURE);
}
}
/* Set supplied input filename or default if not supplied */
if(argc < 4){
if(strnlen(DEFAULT_INPUTFILENAME, MAXFILENAMELENGTH) >= MAXFILENAMELENGTH){
fprintf(stderr, "Default input filename too long\n");
exit(EXIT_FAILURE);
}
strncpy(inputFilename, DEFAULT_INPUTFILENAME, MAXFILENAMELENGTH);
}
else{
if(strnlen(argv[3], MAXFILENAMELENGTH) >= MAXFILENAMELENGTH){
fprintf(stderr, "Input filename too long\n");
exit(EXIT_FAILURE);
}
strncpy(inputFilename, argv[3], MAXFILENAMELENGTH);
}
/* Set supplied output filename base or default if not supplied */
if(argc < 5){
if(strnlen(DEFAULT_OUTPUTFILENAMEBASE, MAXFILENAMELENGTH) >= MAXFILENAMELENGTH){
fprintf(stderr, "Default output filename base too long\n");
exit(EXIT_FAILURE);
}
strncpy(outputFilenameBase, DEFAULT_OUTPUTFILENAMEBASE, MAXFILENAMELENGTH);
}
else{
if(strnlen(argv[4], MAXFILENAMELENGTH) >= MAXFILENAMELENGTH){
fprintf(stderr, "Output filename base is too long\n");
exit(EXIT_FAILURE);
}
strncpy(outputFilenameBase, argv[4], MAXFILENAMELENGTH);
}
/* Set policy if supplied */
if(argc > 5){
if(!strcmp(argv[5], "SCHED_OTHER")){
policy = SCHED_OTHER;
printf("OTHER!\n");
}
else if(!strcmp(argv[5], "SCHED_FIFO")){
policy = SCHED_FIFO;
printf("FIFO!\n");
}
else if(!strcmp(argv[5], "SCHED_RR")){
policy = SCHED_RR;
printf("RR!\n");
}
else{
fprintf(stderr, "Unhandeled scheduling policy\n");
exit(EXIT_FAILURE);
}
}
else{
policy = SCHED_OTHER;
}
printf("argv[5] is: \n", argv[5]);
printf("policy is: %d\n", policy);
/* Set process to max prioty for given scheduler */
param.sched_priority = sched_get_priority_max(policy);
/* Set new scheduler policy */
fprintf(stdout, "Current Scheduling Policy: %d\n", sched_getscheduler(0));
fprintf(stdout, "Setting Scheduling Policy to: %d\n", policy);
if(sched_setscheduler(0, policy, &param)){
perror("Error setting scheduler policy");
exit(EXIT_FAILURE);
}
fprintf(stdout, "New Scheduling Policy: %d\n", sched_getscheduler(0));
/* Set number of processes if supplied */
if(argc > 6){
numProcesses = atoi(argv[6]);
if(numProcesses <= 0){
fprintf(stderr, "Too few processes\n");
exit(EXIT_FAILURE);
}
}
else{
numProcesses = 1;
}
/* Confirm blocksize is multiple of and less than transfersize*/
if(blocksize > transfersize){
fprintf(stderr, "blocksize can not exceed transfersize\n");
exit(EXIT_FAILURE);
}
if(transfersize % blocksize){
fprintf(stderr, "blocksize must be multiple of transfersize\n");
exit(EXIT_FAILURE);
}
/* Allocate buffer space */
buffersize = blocksize;
if(!(transferBuffer = malloc(buffersize*sizeof(*transferBuffer)))){
perror("Failed to allocate transfer buffer");
exit(EXIT_FAILURE);
}
/* Set new scheduler policy */
/* fprintf(stdout, "Current Scheduling Policy: %d\n", sched_getscheduler(0));
fprintf(stdout, "Setting Scheduling Policy to: %d\n", policy);
if(sched_setscheduler(0, policy, &param)){
printf("sched_setscheduler(0, policy, &param) is:%d\n", sched_setscheduler(0, policy, &param));
perror("Error setting scheduler policy");
exit(EXIT_FAILURE);
}
fprintf(stdout, "New Scheduling Policy: %d\n", sched_getscheduler(0));
*/
for(i = 0; i< numProcesses; i++){
id = fork();
printf("id is %d\n", id);
if(id == 0){
/* Open Input File Descriptor in Read Only mode */
if((inputFD = open(inputFilename, O_RDONLY | O_SYNC)) < 0){
perror("Failed to open input file");
exit(EXIT_FAILURE);
}
/* Open Output File Descriptor in Write Only mode with standard permissions*/
rv = snprintf(outputFilename, MAXFILENAMELENGTH, "%s-%d",
outputFilenameBase, getpid());
if(rv > MAXFILENAMELENGTH){
fprintf(stderr, "Output filenmae length exceeds limit of %d characters.\n",
MAXFILENAMELENGTH);
exit(EXIT_FAILURE);
}
else if(rv < 0){
perror("Failed to generate output filename");
exit(EXIT_FAILURE);
}
if((outputFD =
open(outputFilename,
O_WRONLY | O_CREAT | O_TRUNC | O_SYNC,
S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH)) < 0){
perror("Failed to open output file");
exit(EXIT_FAILURE);
}
/* Print Status */
fprintf(stdout, "Reading from %s and writing to %s\n",
inputFilename, outputFilename);
/* Read from input file and write to output file*/
do{
/* Read transfersize bytes from input file*/
bytesRead = read(inputFD, transferBuffer, buffersize);
if(bytesRead < 0){
perror("Error reading input file");
exit(EXIT_FAILURE);
}
else{
totalBytesRead += bytesRead;
totalReads++;
}
/* If all bytes were read, write to output file*/
if(bytesRead == blocksize){
bytesWritten = write(outputFD, transferBuffer, bytesRead);
if(bytesWritten < 0){
perror("Error writing output file");
exit(EXIT_FAILURE);
}
else{
totalBytesWritten += bytesWritten;
totalWrites++;
}
}
/* Otherwise assume we have reached the end of the input file and reset */
else{
if(lseek(inputFD, 0, SEEK_SET)){
perror("Error resetting to beginning of file");
exit(EXIT_FAILURE);
}
inputFileResets++;
}
}while(totalBytesWritten < transfersize);
/* Output some possibly helpfull info to make it seem like we were doing stuff */
fprintf(stdout, "Read: %zd bytes in %d reads\n",
totalBytesRead, totalReads);
fprintf(stdout, "Written: %zd bytes in %d writes\n",
totalBytesWritten, totalWrites);
fprintf(stdout, "Read input file in %d pass%s\n",
(inputFileResets + 1), (inputFileResets ? "es" : ""));
fprintf(stdout, "Processed %zd bytes in blocks of %zd bytes\n",
transfersize, blocksize);
/* Free Buffer */
free(transferBuffer);
/* Close Output File Descriptor */
if(close(outputFD)){
perror("Failed to close output file");
exit(EXIT_FAILURE);
}
/* Close Input File Descriptor */
if(close(inputFD)){
perror("Failed to close input file");
exit(EXIT_FAILURE);
}
break;
}
else if(id > 0){ //parent
printf("Parent is %d\n", id);
int status = 0;
waitpid(id, &status, 0);
}
else{ //error
printf("Error. pid %d is negative\n", id );
}
}
return EXIT_SUCCESS;
}

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A small I/O bound program to copy N bytes from an input file to an output file.

How to write a C Program : A small I/O bound program to copy N bytes from an input file to an output file. May read the input file multiple times if N is larger than the size of the input file in C Programming Language ?

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