读取文件，修改每一行，将其存储到缓冲区中，一次打印所有内容

Question

This is the file:

 line 1
 line 2
 line 3

How to read the file line by line...

Append a suffix to each line..

FILE *fp = fopen ("file", "r");
while (fgets (buffer, sizeof (buffer), fp) != NULL) {

    // append "test" to each line.
    // store the result in a buffer named "result"

}
fclose (fp);

print the result all at once:

printf( "%s", result );

Expected result :

 line 1test
 line 2test
 line 3test

Answer 1

The below program might do the requirement but it is not efficient enough. I am just giving a rough example. Hope this helps.

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

void display(char** temp,int LinesWritten);

int main()
{
FILE *fp;

char *buffer  = (char*)malloc(sizeof(char)*101); // 101 is just an assumption. dynamic size may be decided 
char **result = (char**)malloc(sizeof(char*)*10); // 10 is just an assumption. dynamic size may be decided
int LinesWritten = 0;
char **temp = result;
char **freetemp = result;

if((fp = fopen("file.txt","r"))==NULL)
{
        printf("Error while opening file\n");
        exit(1);
}

while((fgets(buffer,100,fp))&&(!(feof(fp))))     //assuming that 100 characters will be read into the buffer
{
        if(*result = (char*)malloc(sizeof(char)*10))
        {
                sprintf(*result,"%s%s",buffer,"test");
                *result++;
                LinesWritten++;
        }
}

fclose(fp);

display(temp,LinesWritten);

if(freetemp!=NULL)
{
        free(freetemp);
}

return 0;

}

void display(char** temp,int LinesWritten)
{

for(int i=0;i<LinesWritten;i++)
{
        printf("%s\n",*temp);
        *temp++;
}

return;
}