I am new to C programming and I have been trying to make a simple program that reads integers from a .txt file into an array then print it.
The numbers in the file are arranged as follows:
23
44
12
41
123
And this is the code I have been trying:
void main()
{
FILE *fp;
int num[100],i,j;
fopen_s(&fp, "C:/Users/User1/Desktop/NUI/fp.txt", "r");
if (fp == NULL)
{
printf("Can't open file for reading.\n");
}
else
{
for (i = 0; i<5; i = i + 1) {
fscanf_s(fp, "%d", &num[i]);
}
}
for (j = 0; j<5 ; j = j + 1) {
printf("%d\n", num[j]);
}
fclose(fp);
}
In the FOR LOOP I have to write i<5 , j<5 to set number of iterations.But I want to know of there is a way to make the loop recognise the final number automatically.
(Something similar to char[i]!='\0' but for int array)
You can use EOF that means end of file.
In this sample I read the file intFile.txt and print the numbers that I have read.
#include <stdio.h>
int main()
{
FILE * fp;
int numInt[100];
int counter = 0;
fp = fopen ("intFile.txt", "r");
while(fscanf(fp, "%d", &numInt[counter])!= EOF)
{
printf("num = %d\n",numInt[counter++]);
}
fclose(fp);
return 0;
}
Related
I would like to do two Things in my code
1)Write a program to write a two dimensional integer array to a text file.
and
2)Write a second program to read a two dimensional integer array from a text file. The second program should print the matrix on screen. Also to get the filename I should use command line argument.
For example on the cmd the output should be like this:
matrix.txt
8 3 3 1
13 5 31 -8
9 9 0 42
And this is the code which I have made. However only the error message "Can't open matrix.txt" comes out. What is the problem with my code?
#include <stdio.h>
#include <stdlib.h>
#define _CRT_SECURE_NO_WARNINGS
#define ROW 3
#define COL 4
#define FILE_NAME "matrix.txt"
void input_matrix(int matrix[ROW][COL], FILE*);
int main()
{
int Multiarray[ROW][COL];
int i, j;
FILE* fp;
fp = fopen_s(&fp, FILE_NAME, "r");
if (fp == NULL)
{
fprintf(stderr, "Can't open %s\n", FILE_NAME);
exit(EXIT_FAILURE);
}
else
{
input_matrix(Multiarray, fp);
for (i = 0; i < ROW; i++)
{
for (j = 0; j < COL; j++)
{
fprintf(fp, "%d ", Multiarray[i][j]);
}
fprintf(fp, "\n");
}
}
//This part should print out the result of my input
close(fp);
return 0;
}
void input_matrix(int matrix[ROW][COL], FILE* fp)
{
int i, j;
fp = fopen_s(&fp, FILE_NAME, "w");
for (i = 0; i < ROW; i++)
{
for (j = 0; j < COL; j++)
{
fscanf_s(fp, "%d", &matrix[i][j]);
// I have already scanned all the element of my array
}
}
}
Function fopen_s returns 0 on success. As result the program fails on success.
Try:
int ret = fopen_s(&fp, FILE_NAME, "r");
if (ret != 0)
{
fprintf(stderr, "Can't open %s\n", FILE_NAME);
exit(EXIT_FAILURE);
}
I am new to C programming and I am getting a THREAD 1: EXC_BAD_ACCESS(code = 1, address 0x68)
when I run my program. The purpose of my code is to read from a txt file that contains positive and negative numbers and do something with it.
#include <stdio.h>
int main (int argc, const char * argv[]) {
FILE *file = fopen("data.txt", "r");
int array[100];
int i = 0;
int num;
while( fscanf(file, "%d" , &num) == 1) { // I RECEIVE THE ERROR HERE
array[i] = num;
printf("%d", array[i]);
i++;
}
fclose(file);
for(int j = 0; j < sizeof(array); j++){
printf("%d", array[j]);
}
}
After
FILE *file = fopen("data.txt", "r");
Say
if(file == 0) {
perror("fopen");
exit(1);
}
Just a guess, the rest of the code looks ok, so likely this is the problem.
Also worth noting that you might have more than 100 numbers in your file, in which case you will blow past the size of your array. Try replacing the while loop with this code:
for (int i = 0; i < 100 && ( fscanf(file, "%d" , &num) == 1); ++i)
{
array[i] = num;
printf("%d", array[i]);
}
Do you have the file "data.txt" created and local?
touch data.txt
echo 111 222 333 444 555 > data.txt
Check that your file open succeeded.
Here is a working version,
#include <stdio.h>
#include <stdlib.h> //for exit
int main (int argc, const char * argv[])
{
FILE *fh; //reminder that you have a file handle, not a file name
if( ! (fh= fopen("data.txt", "r") ) )
{
printf("open %s failed\n", "data.txt"); exit(1);
}
int array[100];
int idx = 0; //never use 'i', too hard to find
int num;
while( fscanf(fh, "%d" , &num) == 1) { // I RECEIVE THE ERROR HERE
array[idx] = num;
printf("%d,", array[idx]);
idx++;
}
printf("\n");
fclose(fh);
//you only have idx numbers (0..idx-1)
int jdx;
for(jdx = 0; jdx<idx; jdx++)
{
printf("%d,", array[jdx]);
}
printf("\n");
}
I tried to read a file containing an empty box of '*', the error message doesn't get printed, so the file is opened, but the scan doesn't work. I tried to print the count variable, and the value of count is 0. I don't really know where the fault is. Please help... Thanks
the file content that I want to read
int openmap(int file_no){
char filename[32];
char mapp[100][100];
int number;
int count;
int x[100];
int nomor = 1;
for(int i = 1; i <= file_no; i++){
sprintf(filename, "map%d.txt", i);
FILE *test = fopen(filename,"r");
if(test)
{
printf("%2d. Map %d\n", nomor, i);
x[nomor-1] = i;
nomor++;
fclose(test);
}else if(!test && i > file_no){
printf("No map available!");
return 1;
}
}
do{
printf("[0 to cancel] [1 - %d]>> ", nomor-1);
scanf("%d", &number);
}while(number < 0 || number > file_no);
if(number > 0){
sprintf(filename,"map%d.txt", x[number-1]);
printf("%s", filename);
FILE *open = fopen(filename, "r");
if(!open){
printf("error");
}
while(!feof){
fscanf(open, "%[^\n]\n", mapp[count]);
count++;
}
fclose(open);
for(int i = 0; i < count ; i++){
printf("%s\n", mapp[i]);
}
}
}
I created a small test program:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void main () {
char mapp[100][100];
int i, count = 0;
char filename[32];
sprintf(filename, "test.txt");
FILE *open = fopen(filename, "r");
if(!open){
printf("error");
}
while(!feof(open)){
fscanf(open, "%[^\n]\n", mapp[count]);
count++;
}
fclose(open);
for(i = 0; i < count ; i++){
printf("%s\n", mapp[i]);
}
}
as far as i can see the only issue you have regarding the relevant section is your while loop condition, you should use: while(!feof(open)) - i tested my solution and it works so it seems that this is the only issue in your solution
Working on a project where I have to have a file that is generated numbers. First line is a generated int. Followed by a floats (separate lines). (I'm doing it separate lines because I feel it makes more sense as I have to read it two different ways for the bin packing problems which I need this for... Like one way of reading one at a time and another storing it in an array.. But want to get this down first)
Getting a seg fault when I try to read my file for a float after reading an int. Edit: Error occurs in readOffline.
int randomFunction()
{
FILE *fp;
int i;
fp = fopen("theItems.txt", "w" );
if (fp == NULL)
printf("Error: file can't be opened.\n");
srand(time(NULL) );
int random_number = rand();
printf("Random Number %d\n", random_number);
fprintf(fp,"%d",random_number);
fclose(fp);
fp = fopen("theItems.txt", "a");
int numberOfItems = rand();
printf("NumberOfItems: %d\n",numberOfItems);
for(i = 0; i < 10; i++)
{
fp = fopen("theItems.txt", "a");
float number = (float)rand()/(float)(RAND_MAX);
fprintf(fp,"%f",number);
fprintf(fp,"%s", "\n");
fclose(fp);
}
return numberOfItems;
}
void readOffline( int numberOfItems)
{
FILE *fp;
int n = 0,i;
float nu = 0.00;
fp = fopen("theItems.txt", "r");
if (fp == NULL)
printf("Error: file can't be opened.\n");
fseek(fp,SEEK_SET,0);
fscanf(fp,"%d",&n);
printf("Number read: %d\n", n);
float array[numberOfItems];
// for(i = 0; i < 3; i++)
// {
fscanf(fp,"%f",&nu);
// array[i] = nu;
// }
fclose(fp);
printf("Int:%d\n", n);
int j;
// for(j = 0; j < 3; j++)
// printf("Float Number:%f\n", array[j]);
}
int main()
{
int numberOfItems = randomFunction();
readOffline(numberOfItems);
return 0;
}
Just trying to get an understanding why it causes a seg error when I // it out I can get it to read my int but sometimes it isn't the right int read. But yeah.
Please let me know if I need any more details or need to be more clear anywhere
You have multiple issues in your code:
You open the output file multiple times in randomFunction(), you even leak a stream handle and leave it open.
You do not exit the function when fopen() returns NULL. The rest of the code invokes undefined behavior if fp == NULL.
The same problem is present in readOffline(): if fp == NULL, you should return from the function immediately.
you do not output a linefeed after the first random number in the output file.
you always output 10 random numbers.
most importantly: the random number returned by the randomFunction() is potentially huge, allocating an array with local storage larger than a few megabytes is likely to cause undefined behavior. Try and reduce the maximum random number of values.
Here is a proposed correction:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int randomFunction(void) {
FILE *fp;
int i;
fp = fopen("theItems.txt", "w");
if (fp == NULL) {
printf("Error: file can't be opened.\n");
return -1;
}
srand(time(NULL));
int random_number = rand();
printf("Random Number %d\n", random_number);
fprintf(fp, "%d\n", random_number);
int numberOfItems = 1 + rand() % 100; /* between 1 and 100 */
printf("NumberOfItems: %d\n", numberOfItems);
for (i = 0; i < numberOfItems; i++) {
float number = rand() / (float)(RAND_MAX);
fprintf(fp, "%f\n", number);
}
fclose(fp);
return numberOfItems;
}
void readOffline(int numberOfItems) {
FILE *fp;
int n = 0, i;
fp = fopen("theItems.txt", "r");
if (fp == NULL) {
printf("Error: file can't be opened.\n");
return;
}
fscanf(fp, "%d", &n);
printf("Number read: %d\n", n);
float array[numberOfItems];
for (i = 0; i < numberOfItems; i++) {
if (fscanf(fp, "%f", &array[i]) != 1)
break;
}
fclose(fp);
printf("Int:%d\n", n);
for (int j = 0; j < i; j++) {
printf("Float Number %d: %f\n", j, array[j]);
}
}
int main(void) {
int numberOfItems = randomFunction();
readOffline(numberOfItems);
return 0;
}
Note that I kept your semantics: the random number at the start of the file is not the number of floating point values that follow. I suspect it should be?
I would say that depending on the particular compiler that you are using, then this could be a problem in setting up the actual array. This is (as an example) discussed in Variable Sized Arrays vs calloc in C From the discussions, you should use calloc and free. Another point is that you need to make sure that your value is greater than 3 and not too big. Since the array is only in the local scope of readOffline(), you should not connect it to the variable numberOfItems.
float array[3];
for(i = 0; i < 3; i++)
{
fscanf(fp,"%f",&nu);
array[i] = nu;
}
I am new to C programming and I am getting a THREAD 1: EXC_BAD_ACCESS(code = 1, address 0x68)
when I run my program. The purpose of my code is to read from a txt file that contains positive and negative numbers and do something with it.
#include <stdio.h>
int main (int argc, const char * argv[]) {
FILE *file = fopen("data.txt", "r");
int array[100];
int i = 0;
int num;
while( fscanf(file, "%d" , &num) == 1) { // I RECEIVE THE ERROR HERE
array[i] = num;
printf("%d", array[i]);
i++;
}
fclose(file);
for(int j = 0; j < sizeof(array); j++){
printf("%d", array[j]);
}
}
After
FILE *file = fopen("data.txt", "r");
Say
if(file == 0) {
perror("fopen");
exit(1);
}
Just a guess, the rest of the code looks ok, so likely this is the problem.
Also worth noting that you might have more than 100 numbers in your file, in which case you will blow past the size of your array. Try replacing the while loop with this code:
for (int i = 0; i < 100 && ( fscanf(file, "%d" , &num) == 1); ++i)
{
array[i] = num;
printf("%d", array[i]);
}
Do you have the file "data.txt" created and local?
touch data.txt
echo 111 222 333 444 555 > data.txt
Check that your file open succeeded.
Here is a working version,
#include <stdio.h>
#include <stdlib.h> //for exit
int main (int argc, const char * argv[])
{
FILE *fh; //reminder that you have a file handle, not a file name
if( ! (fh= fopen("data.txt", "r") ) )
{
printf("open %s failed\n", "data.txt"); exit(1);
}
int array[100];
int idx = 0; //never use 'i', too hard to find
int num;
while( fscanf(fh, "%d" , &num) == 1) { // I RECEIVE THE ERROR HERE
array[idx] = num;
printf("%d,", array[idx]);
idx++;
}
printf("\n");
fclose(fh);
//you only have idx numbers (0..idx-1)
int jdx;
for(jdx = 0; jdx<idx; jdx++)
{
printf("%d,", array[jdx]);
}
printf("\n");
}