Read Text line by line and assign variables per line

Question

I have accomplished getting my c program to read text line by line. That was the easy part or at least in my perspective. What i need to do now is to assign variables per line. For Example the first line of the text file would be equal to the variable line1.

Or this

char line1 = (text from line one)
char line2 = (text from line two)

My code thus far:

    char line[1000] = ""; 

    FILE *ifp;

    ifp = fopen("Tree-B.txt", "r");
    if (ifp == NULL)
    {
        printf("Error opening file!\n");
        exit(1);
    }

    while (fscanf(ifp, "%s", line) == 1)
    {
        printf("%s ", line);
    }
    printf("\n");
    fclose(ifp);

    return 0;

I have absolutely no idea how to do this.

You need to allocate with `malloc()` or use an array `line[1000][1000]`, but this is limited to 1000 lines and 999 characters. — Stargateur, Jan 26 '17 at 02:32
[reading a file to array of strings](http://stackoverflow.com/questions/24908603/reading-a-file-to-array-of-strings) — BLUEPIXY, Jan 26 '17 at 02:35
`fscanf(ifp, "%s", line)` does not save spaces. More useful for reading words than lines. Could use `fgets()` instead. — chux - Reinstate Monica, Jan 26 '17 at 02:41
@Mohsen_Fatemi 999 is the maximum width of characters to read and save. After reading, a null character is appended, hence 1000 `char` needed. — chux - Reinstate Monica, Jan 26 '17 at 02:43

score 1 · Answer 1 · edited May 23 '17 at 11:52

You can use an array of pointer for that matter.

char line[1000] = "";  // assume each line has at most 999 chars (1 space for NUL character)
char *lines[1000] = { NULL }; // assume max number of lines is 1000
int idx = 0;
FILE *ifp;

ifp = fopen("q2.cpp", "r");
if (ifp == NULL)
{
    printf("Error opening file!\n");
    exit(1);
}

while(fgets(line, sizeof(line), ifp) != NULL)
{
    lines[idx] = strdup(line);
    printf("%s", lines[idx]);
    idx++;
}

Notes:

This approach using strdup which is POSIX (not official C standard). However, you can put in a publicly available strdup function itself.
fgets is preferred than fscanf so I changed it that way.
1000 limis are suggestive - you can/should change those constants to what would make more sense in the program itself.

score 0 · Answer 2 · edited May 23 '17 at 12:09

#include <stdio.h>

#define MAX_LINES 1000
#define MAX_LINE_LENGTH 200

int main()
{
    char fileContents[MAX_LINES][MAX_LINE_LENGTH];
    int lineCount = 0;

    FILE *ifp = fopen("Tree-B.txt", "r");
    if (ifp == NULL)
    {
        printf("Error opening file!\n");
        exit(1);
    }

    while (fgets(fileContents[lineCount++], MAX_LINE_LENGTH, ifp) != NULL);
    fclose(ifp);

    printf("File Contents:\n");
    for (int i = 0; i < lineCount-1; ++i)
    {
        printf("%s", fileContents[i]); // or fputs
    }

    return 0;
}

You can refer here, if you wish to dynamically allocate memory for fileContents.

Read Text line by line and assign variables per line

2 Answers2