Read any length of line from file and count the total number of lines in the file

• Download source code - 2.47 KB

Introduction

In the past, if you wanted to read files, there was a restriction. You can not predict how long a line can be present at the read time. So the user has to predict the maximum length of a line that a file could store. But now, using this code, you can read any length of line from your file.

Background

During some programming situation, I needed to read a single line from a text file. At that time, I predicted that the maximum line length would be 1024 or 2048 characters long.

Using the code

Here is the ReadLine function code:

//

int ReadLine(char** pszBuffer, FILE * pFilePtr)
{
    char szBuffer[1024] = {0};   //Temporary Line Buffer
    char *pcRes         = NULL;  //Result of Line Reading
    int   nNl           = 0;     //Length of Line


    //If original buffer is already contains some content, then free it.

    if(*pszBuffer != NULL){
        free(*pszBuffer);
    }

    //allocate some memory 

    *pszBuffer = (char *) malloc(sizeof(szBuffer) + 1);
    **pszBuffer = '\0';
    //Read until new line character is not found in line

    while((pcRes = fgets(szBuffer, sizeof(szBuffer), pFilePtr))  != NULL){
        //Realloc buffer to adjust buffer size

        *pszBuffer = realloc(*pszBuffer, strlen(szBuffer) + 
                                         strlen(*pszBuffer) + 1);
        //if allocation fails

        if(*pszBuffer == NULL){
            printf("\n Memory error");
            return 0;
        }
        //append string to line buffer

        strcat(*pszBuffer, szBuffer);
        strcpy(szBuffer, "");
        nNl = strlen(*pszBuffer) - 1;
        //if end of line character is found then exit from loop

        if((*pszBuffer)[nNl] == '\n'){
            break;
        }
    }
    return 1;
}
//