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Reading a File Line By Line

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Dave Sinkula Dave Sinkula is offline

Offline Jan 12th, 2005, 4:45 pm |

While not terribly difficult, first timers may not know the functions to look up and use. Here is some basic code for reading a file one line at a time. The contents of the file are printed to the stdout.

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#include <stdio.h>
 
int main ( void )
{
   static const char filename[] = "file.txt";
   FILE *file = fopen ( filename, "r" );
   if ( file != NULL )
   {
      char line [ 128 ]; /* or other suitable maximum line size */
 
      while ( fgets ( line, sizeof line, file ) != NULL ) /* read a line */
      {
         fputs ( line, stdout ); /* write the line */
      }
      fclose ( file );
   }
   else
   {
      perror ( filename ); /* why didn't the file open? */
   }
   return 0;
}
 
/* file.txt
This text is the contents of the file named, "file.txt".
 
It is being used with some example code to demonstrate reading a file line by
line. More interesting things could be done with the output, but I'm trying to
keep this example very simple.
*/
 
/* my output
This text is the contents of the file named, "file.txt".
 
It is being used with some example code to demonstrate reading a file line by
line. More interesting things could be done with the output, but I'm trying to
keep this example very simple.
*/

Code Snippet Comments

khuman_nb

Offline | Feb 9th, 2006

•

I thinks instead of depending on the length of the line (which can be variable depeding on the type of editor and its settings).I think it'll be better to look for '\n' which is line separator.

Dave Sinkula Dave Sinkula is offline

Offline | Mar 19th, 2006

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I thinks instead of depending on the length of the line (which can be variable depeding on the type of editor and its settings).I think it'll be better to look for '\n' which is line separator.

Then you would be describing doing this "by character" rather than by line. Otherwise you are wonderfully overcomplicating this with dynamic memory allocation a la C++'s std::string.

darylcharm darylcharm is offline

Offline | Aug 24th, 2006

•

hi this is great!

can you tell me how do i put each line to an array?

Tmo

Offline | Jan 8th, 2007

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hi guys
i just modified the one i got here: this will read line by line from a text file then stored every line to an array;

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <conio.h>
#include <ctype.h>
#include <ctype.h>
#include <time.h>
#include <sys/types.h>

int main ( void )
{
static const char filename[] = "data.txt";
FILE *file = fopen ( filename, "r" );
int i, j;
char arra[128][128];
char line[128]; /* or other suitable maximum line size */

for(i=0; i<128; i++)
for(j=0; j<128; j++)
arra[i][j] = '\0';

for(i=0; i<128; i++)
line[i] = '\0';

if ( file != NULL )
{

i=0;

while ( fgets ( line, sizeof line, file ) != NULL ) /* read a line */
{

strcpy(arra[i], line);
printf("array ----> %s ", &arra[i]);
i++;

}
fclose ( file );
}
else
{
perror ( filename ); /* why didn't the file open? */
}

return 0;
}

tirmizi

Offline | Nov 12th, 2008

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i want to Read a line from file then compare it to a sentense(GPS Sentence) and if its match(valid) then display this line else display Error

plz advice
Regards