I wrote this code where I generate random integers in a large quantity and store them in a txt file. it works if I input up to 49 integers
but after that it does not read any further from the file or the file don't accept any further I don't know please help me
this is the code
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
FILE *fptr;
int num, n;
fptr = fopen("integers.txt", "w");
if (fptr != NULL)
{
printf("File created successfully!\n");
}
else
{
printf("Failed to create the file.\n");
return -1;
}
printf("Enter some integer numbers [Enter -1 to exit]: ");
scanf("%d", &n);
while (n != 0)
{
num = rand();
putw(num, fptr);
n--;
}
fclose(fptr);
fptr = fopen("integers.txt", "r");
printf("\nNumbers:\n");
int count = 0;
while ((num = getw(fptr)) != EOF)
{
printf("%d\n", num);
count++;
}
printf("\nNumber of elements in the file %d",count);
fclose(fptr);
return 0;
}
You have following problems:
As you're writing binary data, the file needs to be opened with "wb" and "rb" (b stands for binary). Othwerwise certain unwanted text substitutions will take place.
If one of your random numbers turns out to be -1, the read will stop prematurely because EOF has the value -1. Therefore you need to do the end of file check with the feof function instead of comparing the value read with EOF.
fptr = fopen("integers.txt", "wb"); // <<< open with binary mode "wb"
...
fptr = fopen("integers.txt", "rb"); // <<< open with binary mode "rb"
printf("\nNumbers:\n");
int count = 0;
while (1)
{
num = getw(fptr);
if (feof(fptr)) // end of file reached => stop the loop
break;
printf("%d\n", num);
count++;
}
BTW:
The documentation of getw concerning the return value is pretty misleading, especially the part "A return value of EOF indicates either an error or end of file" seems wrong to me. getw can read -1 values (0xffffffff) without problems.
Trying to create a program that takes in a text file and reads it line by line. It then finds the two integers that are on each line and adds them together. It then outputs the new line with the original string and total to a new text file. I need help adding the two integers, getting them from each line, and then putting the new line to a text file.
input text file
good morning hello 34 127
ann 20 45
10 11
fun program and you find the same 90 120
news paper said that 56 11
how do you like 20 5
line number 90 34
Outputs first like would look like: and then continue on
good morning hello 161
Code:
int processTextFile(char * inputFileName, char * outputFileName)
{
FILE *fp = fopen(inputFileName, "r");//open file to to read
char buff[1024];
char *p, *p1;
int num;
while (fgets(buff, 1024, fp)!=NULL)
{
printf("%s\n", buff);
while(scanf(buff, "%*[^0-9]%d", &num)== 1)
printf("%d\n", num);
//fscanf(fp, "%s", buff);
}
return 0;
}
EDIT!!!!::
So now that I've been able to accomplish this. How would I sort it by the number produced? for example:
Time is money 52
here I am 3
21
Would output to a new text file in order like
here I am 3
21
Time is money 52
My version using strcspn() is supposed to work with stdin for input and stdout for output. (so you can do executable <textfile >newtextfile)
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char line[1000];
while (fgets(line, sizeof line, stdin)) {
char *ptr;
size_t x = strcspn(line, "0123456789");
if (line[x]) {
errno = 0;
int n1 = strtol(line + x, &ptr, 10);
if (*ptr && !errno) {
errno = 0;
int n2 = strtol(ptr, &ptr, 10);
if (*ptr && !errno) {
int n3 = n1 + n2;
printf("%.*s%d\n", (int)x, line, n3);
} else {
printf("%s", line); // line includes ENTER
}
} else {
printf("%s", line); // line includes ENTER
}
} else {
printf("%s", line); // line includes ENTER
}
}
return 0;
}
The same version without the error checking
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char line[1000];
while (fgets(line, sizeof line, stdin)) {
char *ptr;
size_t x = strcspn(line, "0123456789");
int n1 = strtol(line + x, &ptr, 10);
int n2 = strtol(ptr, &ptr, 10);
int n3 = n1 + n2;
printf("%.*s%d\n", (int)x, line, n3);
}
return 0;
}
The approach should be:
open two files, one for input, one for output.
use sscanf() to read the input buffer.
scan the leading string, and then two number.
if previous sscanf() fails, only check for two number.
if either of the above scanning is success, print the sum to the output file.
A sample code, should look like
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
FILE *fpin = fopen("ipfile", "r");//open file to to read
if (!fpin)
{
printf("Error in ipfile opening\n");
exit (-1);
}
FILE *fpout = fopen("opfile", "w");//open file to to write
if (!fpout)
{
printf("Error in opfile opening\n");
exit (-1);
}
char buff[1024] = {0};
char str[1024] = {0};
int num1 =0, num2= 0;
while (fgets(buff, 1024, fpin)!=NULL)
{
memset(str, 0, sizeof(str));
//printf("%s\n", buff);
if(sscanf(buff, "%[^0-9]%d %d", str, &num1, &num2)== 3)
fprintf(fpout, "%s %d\n", str, (num1+num2));
else if (sscanf(buff, "%d %d", &num1, &num2)== 2)
fprintf(fpout, "%d\n", (num1+num2));
}
return 0;
}
Note:
The above procedure, is a kind of workaround. If the data pattern in the file changes, lot of changes will be required to maintain a code like that. Instead of usinf sscnaf(), for a better and roubust approach, you should
read the line from file
start tokenizing the input buffer (strtok()) and check for ints as tokens (strtol()).
save the returned tokens and ints seperately.
once the strtok() returns NULL, you print the string tokens and the sum of the ints to the o/p file.
I intend not to change your code completely, so I just added some snippets for improvement.
int processTextFile(char *inputFileName, char *outputFileName) {
FILE *fp = fopen(inputFileName, "r");
FILE *out = fopen(outputFileName, "w");
char line[1024];
if (!fp) {
perror(inputFileName);
return;
}
while (fgets(line, sizeof(line), fp) != NULL) {
int num1 = 0, num2 = 0;
char textPart[1024] = "";
if ( !sscanf(line, "%[a-zA-Z' ']%d%d", textPart, &num1, &num2) {
sscanf(line, "%d%d", &num1, &num2);
}
fprintf(out, "%s %d\n", textPart, num1 + num2);
}
fclose(fp);
fclose(out);
}
Explanation:
I scanned the text file, extracted the text part and the two ints. Since I noticed that the ints are placed at the end of each line, I just used sscanf() for that matter.
sscanf(line, "%[a-zA-Z' ']%d%d", textPart, &num1, &num2);
Here, "%[a-zA-Z' ']%d%d" format specifiers means to get only alphabets and spaces.
Since it will only get letters and spaces, the line "10 11" in your input file won't be put to num1 and num2. Because the code inspects first for a string containing letters and spaces. Since 10 and 11 are not of the qualified types, then the line is just skipped.
That's why I added an if-else statement, which checks if sscanf wrote anything to memory. If sscanf returned 0, then it means that no text part is present. Just digits. So the program will scan the two digits.
if ( !sscanf(line, "%[a-zA-Z' ']%d%d", textPart, &num1, &num2) ) {
sscanf(line, "%d%d", &num1, &num2);
}
I also added file checking for input file. It checks if file doesn't exist or can't be opened by the filestream.
if (!fp) {
perror(inputFileName);
return;
}
Here is the content of output file after execution:
good morning hello 161
ann 65
21
fun program and you find the same 210
news paper said that 67
how do you like 25
line number 124
so I have this file called "score.txt" with contents
NAME
20
NAME2
2
And I'm using this code but it gets an error and I have no idea on how to put the integers from the file in an array.
int main(){
FILE* file = fopen ("score.txt", "r");
int i = 0;
fscanf (file, "%d", &i);
while (!feof (file))
{
printf ("%d ", i);
fscanf (file, "%d", &i);
}
fclose (file);
system("pause");
}
I'm only self learning and i've been trying to figure this out for 2hours already
The problem with using fscanf for input where some lines will fail the format is that the file will not be advanced per iteration of the while loop, so you get stuck.
You can get a solution by using fgets to grab the data and sscanf to grab the number:
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
int main(void) {
int i = 0;
int ret = 0;
char buf[50];
FILE *file = fopen("score.txt", "r");
if (file == NULL) {
fprintf(stderr,"Unable to open file\n");
exit(1);
}
while (fgets(buf,sizeof(buf),file)) {
ret = sscanf(buf,"%d",&i);
if (ret == 1) { // we expect only one match
printf("%d\n", i);
} else if (errno != 0) {
perror("sscanf:");
break;
}
}
fclose(file)
return(0);
}
This will output, for your input:
20
2
We check the output of sscanf as it tells us if the format has been matched correctly, which will only happen on the lines with integer, and not the 'NAME' lines. We also check for 'errno' which will be set to non-zero if sscanf encounters an error.
We used char buf[50]; to declare a char array with 50 slots, which fgets then uses to store the line its reading; however if the line is more than 50 chars in length it will be read in 50 char chunks by fgets, and you may not get the results you desire.
If you wish to store the integers you read into an array, you'll have to declare an array, then on each read assign a slot in that array to the value of the int you read i.e. int_array[j] = i (where j will have to change with each slot you use). I'll leave it as an exercise to implement this.
I have recently learnt about using I/O files in C, and one of my book exercises asks me to read lines of pairs of number and add them, then print them to an output file.
What I mean is:
If the input file looks like:
12 13
24 26
23 13
the output file will be:
25
50
36
I have tried reading it as a string using:
fscanf(in, "%s", &string); //in is the input file pointer
but it doesn't work (causes a seg. fault)
My problem is that I am unable to take in the lines of pairs of numbers using the fscanf function, as I do not know how many lines there are in the input file.
Thus, my question is: How do I read an input file containing an amount of lines if I do not know how many lines there are? Can I read it as a string?
Thank you in advanced.
Michael
Here's some working code:
#include <stdio.h>
#include <conio.h>
main()
{
int a,b;
FILE *fp = fopen("filename.txt", "r"); //open file for reading
FILE *f = fopen("file.txt", "w"); //open file for writing
while (!feof (fp)) //reading file until end of file
{
fscanf (fp, "%d", &a);
fscanf (fp, "%d", &b);
int sum = a + b;
fprintf(f, "%d\n", sum); //writing summation to a file
}
fclose(f); //close files
fclose(fp);
return 0;
}
Just create filename.txt and write numbers in it. And create blank file.txt.
I've written the following snippet to write n random numbers to a file. After writing, I read from the file and store the numbers in an array. The problem I'm facing is that when I read from the file I get extra numbers.
#include<stdio.h>
#include<stdlib.h>
int main(void)
{
int limit,i=0;
int numbers[100];
char line[100];
printf("Enter the number of random number to be generated(max 1000)");
scanf("%d",&limit);
FILE *fpi;
fpi=fopen("input.txt","w");
for(i=0;i<limit;i++)
{
fprintf(fpi,"%d\n",rand());
}
fclose(fpi);
FILE *file;
file = fopen("input.txt", "r");
while(fgets(line, sizeof line, file)!=NULL)
{
numbers[i]=atoi(line);
i++;
}
printf("%d\n\n",i);
int totalNums = i;
for (i=0 ; i<totalNums ; i++)
{
printf("%d\n",numbers[i]);
}
fclose(file);
return 0;
}
If I give limit=3 and I write 3 numbers to the file, eg.47,18836,431.
When I read from the file and print it I get 6 values out of which the first 3 are junk and the next 3 are the ones that were written.
If I comment out the writing part and just try to read from the file I get the correct output of only 3 numbers. So I think that there is some problem in my code that writes to the file part.
Can someone help me out with it.
Reset i to 0 before reading from file. e.g.
//your code before
i=0; //reset i
while(fgets(line, sizeof line, file)!=NULL)
{
numbers[i]=atoi(line);
i++;
}
//your code after