How to read text from file into Array

Question

I am trying to understand how to read some file from text, and then enter it into an array to save it for later manipulation. I just cant seem to get it. I have tried structs and string arrays but I still cant grasp how to implement this in c. I have successfully been able record at least one line into the array but it copies the same line multiple times. Here is a layout of what my text and code look like.

Text File:

# A demonstration of some simple MIPS instructions

Loop: sll $t1, $s3, 2
      add $t1, $t1, $s6
      lw $t0, 0($t1)
      bne $t0, $s5, Exit
      addi $s3, $s3, 1
      j Loop
Exit:

.c File:

int assem::readFile(FILE *file) //read file function for file to be read
{
//char String[200];
char lines[20];
char *ptr = lines;
const int MAX = 101;
char myString[MAX];
int i = 0;

while(fgets(&lines[i], 100, file) != NULL)
{
    i++;
}

printf("%s\n", lines);

regarding this line: 'int assem::readFile(FILE *file)' class::method() is C++, not C — user3629249
– user3629249, Commented Jul 24, 2015 at 5:04

mazhar islam · Accepted Answer · 2015-07-23 08:48:41Z

char * fgets ( char * str, int num, FILE * stream );

fgets() reads characters from stream and stores them as a C string into str until (num-1) characters have been read or either a newline or the end-of-file is reached, whichever happens first.

I have successfully been able record at least one line

Because a newline character makes fgets stop reading. See reference here.

You can use

size_t fread ( void * ptr, size_t size, size_t count, FILE * stream );

to read from a file.

fread() reads an array of count elements, each one with a size of size bytes, from the stream and stores them in the block of memory specified by ptr.

I write the following function to read from a file and write each character into a buffer, which may help you:

typedef  unsigned char BYTE;
void readFile(char *filename, BYTE* buffer) {
    FILE * pFile;
    long lSize;
    size_t result;

    pFile = fopen(filename, "rb");
    if (pFile == NULL ) {
        fputs("File error", stderr);
        exit(1);
    }

    // obtain file size:
    fseek(pFile, 0, SEEK_END);
    lSize = ftell(pFile);
    rewind(pFile);

    // copy the file into the buffer:
    result = fread(buffer, 1, lSize, pFile);
    if (result != lSize) {
        fputs("Reading error 2", stderr);
        exit(3);
    }

    /* the whole file is now loaded in the memory buffer. */
    fclose(pFile);
}

Richard Dally · Accepted Answer · 2015-07-24 08:16:11Z

1

Here's a simple code to statically store 10 lines containing 99 characters (don't forget \0 to terminate a string)

const size_t maxLines = 10;
size_t currentLine = 0;
char lines[maxLines][100]; // Storing 10 lines

// Reading and storing a line from file
while(fgets(lines[currentLine], sizeof(lines[currentLine]), file) && currentLine < maxLines)
{
    ++currentLine;
}

// Printing stored lines
size_t i = 0;
while (i < currentLine)
{
    printf("%s", lines[i]);
    ++i;
}

edited Jul 24, 2015 at 8:16

answered Jul 23, 2015 at 8:46

Richard Dally

1,4582 gold badges22 silver badges40 bronze badges

1 Comment

user3629249 Over a year ago

for robustness, this line: 'while(fgets(lines[currentLine], sizeof(lines[currentLine]), file))' should probably be: 'while(( fgets(lines[currentLine], sizeof(lines[currentLine]), file)) && currentLine < 10)'

Sagi Sulimani · Accepted Answer · 2015-07-23 10:00:24Z

0

You need to read all the file character by character. It will make it easier.

#include <stdio.h>
void main ()
{
    int ch, size, i = 0;
    FILE *file;
    file = fopen("Text.txt", "r"); // open the file for reading
    fseek(file, 0L, SEEK_END);  // goto the end of the file
    size = ftell(file);
    rewind(file);               // goto the start of the file
    char *text = (char*)malloc(size - 20);  // the -20 is to avoid the gibberish at the end of the text file

    for (i = 0; i<size; i++)
    {
       ch = fgetc(file);
       text[i] = ch;
    }
    printf("%s", text);
    getchar();
}

answered Jul 23, 2015 at 10:00

Sagi Sulimani

868 bronze badges

Comments

Tiggity Tank · Accepted Answer · 2015-07-23 11:24:02Z

-1

Thanks for the help> i managed to solve figure out how to do it a bit earlier. Here is my implementation after I finally understood a few more c literals. Thanks AGAIN!!! "counter" keeps track of how many lines are in the text file

int assem::readFile(FILE *file) 
{
int i =0;
counter = 0;                                            //this is sort of the constructor, if you will. 
                                                        //breaks down text file into line by line 
while(fgets(myString, 101, file) != NULL)               //and stores them into "myLines array"
    {
        myLines[i] = strdup(myString);
        i++;
        counter++;
    }   

return 0;
}

answered Jul 23, 2015 at 11:24

Tiggity Tank

115 bronze badges

2 Comments

user3629249 Over a year ago

this answer fails to define myLines and myString and myLines now should to be defined as 'char ** myLines = malloc(...);'

Tiggity Tank Over a year ago

thanks for the feedback. myLines and myString were both defined in the head class file

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