How to make a C program that can read a data and copy some in a variable?

Question

I'm a student, I am wondering... How can I make a program that can Get some data from my text file to a variable on my program and print them

Example:

My Text File

I,Ate,Cookies
She,Drink,Coffee
Tom,Wears,Pyjamas

My code

main()
{
    FILE *fp=fileopen("c:\\textfile.txt","r");
    char name[20],action[20],item[20];
    prinf("Enter name: \n");
    scanf("%s",&name);

    /* I dont Know what to do next */
}

I though about some checking code:

if (name==nametxt)  /*nametxt is the first line on the text file */
{
    printf("%s\n %s\n %s\n",name,action,item);
}

If the name is "I",the output would look like this :

 Enter name:
 I
 I
 Eat
 Cookies

A help will satisfy my curiosity thanks in advance

First, read this documentation : http://devdocs.io/c/io/fread. — Freddykong, Aug 16 '17 at 14:29
yes, you could use `fscanf` to read comma-delimited records... — Antti Haapala -- Слава Україні, Aug 16 '17 at 14:37
https://stackoverflow.com/questions/15091284/read-comma-separated-input-with-scanf — Antti Haapala -- Слава Україні, Aug 16 '17 at 14:37

Quentin · Answer 1 · 2017-08-16T15:28:54.097

0

There is different ways to read data from a FILE * in C :

You read only one character : int fgetc(FILE *fp);.
You read a whole line : char *fgets(char *buf, int n, FILE *fp); (take care to buf, it must point to allocate memory).
You read a formatted string, which is your case here : int fscanf(FILE *stream, const char *format, ...), it works like printf() :

This way :

char name[20], action[20], item[20];
FILE *f = fopen("myfile.txt", "r");

if (! f)
    return;

if (3 == fscanf(f, "%19[^,\n],%19[^,\n],%19[^,\n]\n", name, action, item))
    printf("%s %s %s\n", name, action, item)

%30[^,\n], here is used to read of whole object of your line, except , or \n, which will read item by item the content of your string.

edited Aug 16 '17 at 15:28

answered Aug 16 '17 at 14:33

Quentin

724
7
16

`%s` reads a space delimited string, not a comma-delimited string. – Antti Haapala -- Слава Україні Aug 16 '17 at 14:35
@BLUEPIXY Exact, I fixed it. – Quentin Aug 16 '17 at 15:30
now i do have a code, but, i cant get what i want from the txt file like – Archie Aug 17 '17 at 12:43

score 0 · Accepted Answer · answered Aug 16 '17 at 14:38

You are reading characters from file until you receive new line character (\n) or fill an array, then you return characters stored in an array passed by caller.
From this returned array you may get separated values with strtok.
Repeat until you receive 0 from getline (Getline received EOF from file.)

Here is simple example with your own getline function which you may modify.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int getline(char s[],int lim, FILE * fp)
{
    int c, i;
    for (i=0; i < lim-1 && (c=fgetc(fp))!=EOF && c!='\n'; ++i)
    {
        s[i] = c;
    }
    if (c == '\n')
    {
        s[i] = c;
        ++i;
    }
    s[i] = '\0';
    return i;
}

int main()
{
    FILE * fp = fopen("c:\\textfile.txt", "r");

    char line[100];
    char * ptr;

    while (getline(line, 100, fp))
    {
        ptr = strtok(line, ",");

        while( ptr != NULL )
        {
           printf(" %s\n", ptr);

           ptr = strtok(NULL, ",");
        }
    }

    return 0;
}

Output

I
Ate
Cookies

She
Drink
Coffee

Tom
Wears
Pyjamas

Storing strings into variable isnt tough, here is an example

strcpy(name, ptr);

But be careful, writing outside of bounds have undefined behavior.

strncpy(name, ptr, 100); You can limit number of copied characters with strncpy, but be careful, this function is error-prone.

score 0 · Answer 3 · answered Aug 16 '17 at 14:40

You can do like this,

Go on reading characters from a file, after every character is read compare with ',' character.
If the character read is ',' then you have finished reading the name, otherwise store it in a character array and continue reading the file.
Once you hit ',' character, terminate the character array with null character(Now you have a complete name with you).
Compare this character array with a string you receive as input using a strcmp(String compare function). If its it matches decide what you wanna do?

I hope i am clear.

BLUEPIXY · Answer 4 · 2017-08-16T16:12:02.747

start with like this

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define DATA_FILE "data.txt"
#define LEN 19
#define SIZE (LEN+1)
//Stringification
#define S_(n) #n
#define S(n) S_(n)

enum { NOT_FOUND, FIND };

int pull_data(const char name[SIZE], char action[SIZE], char item[SIZE]){
    int ret = NOT_FOUND;

    FILE *fp = fopen(DATA_FILE, "r");//fileopen --> fopen
    if(fp == NULL){
        perror("fopen:");
        exit(EXIT_FAILURE);
    } else {
        char nametxt[SIZE];
        *action = *item = 0;
        while(fscanf(fp, "%" S(LEN) "[^,],%" S(LEN) "[^,],%" S(LEN) "[^\n]%*c", //"%19[^,],%19[^,],%19[^\n]%*c"
            nametxt, action, item) == 3){
            if(strcmp(name, nametxt) == 0){//Use strcmp for comparison of strings
                ret = FIND;
                break;
            }
        }
    }
    fclose(fp);
    return ret;
}

int main(void){
    char name[SIZE], action[SIZE], item[SIZE];

    printf("Enter name: \n");//prinf --> printf
    if(scanf("%" S(LEN) "s", name) == 1){
        if(pull_data(name, action, item) == FIND){
            printf("%s\n%s\n%s\n", name, action, item);
        } else {
            printf("%s not found.\n", name);
        }
    }
}

How to make a C program that can read a data and copy some in a variable?

My Text File

My code

4 Answers4