Reading a File Line By Line

2

By Dave Sinkula on Jan 13th, 2005 2:45 am

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.

#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.
*/

7 Years Ago

0

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.

khuman_nb

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7 Years Ago

0

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.

Dave Sinkula

long time no c

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6 Years Ago

0

hi this is great!

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

darylcharm

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6 Years Ago

0

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[j] = '\0';


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


if ( file != NULL )
{


i=0;


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


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


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



return 0;
}

Tmo

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4 Years Ago

0

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

tirmizi

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4 Years Ago

0

thanks for this code this is just what im looking for..:D

Dionysus

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2 Years Ago

0

Im very much thankful to you for providing the coding for me

swaythi

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2 Years Ago

0

thank you for the code..!!![/COLOR]

swaythi

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2 Years Ago

0

I tried using this code, but it gives a segmentation error when trying to read the last line of the file

bojomojo

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1 Year Ago

-1

may be you should avoid placing a newline character twice at the end of the file.
coz after the new line character it will try to read the next line but the fileEnd comes up

kanishka.keshav

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1 Year Ago

0

Good Afternoon, i would like to ask you a question.

I have got file which structured as
"point id" "x coordinates" "y coordinates" "z coordinates"

I would like to open file and search for point id then if point exist in the file
I would like to use x,y and z coordinates of the point.

I will call 4 point like that and calculate the cross-section point coordinates
then write it on file by giving point id by user.

and I also would like to chech if the point id giving by user is exist in the file too.

I dont need the calculation part, i will match variables to x1,y1,z1, ..... x4,y4,z4,
and calculate x5,y5,z5 but i couldnt manage other things.

I will be glad to have any help.

zoidac

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10 Months Ago

0

thank

'CoffeeLike

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