trouble reading data from a file

hi i am trying to read data from a file which is arranged as follows

item1
item2
item3
etc
etc
etc

i am trying to read this then reproduce it on the console window line by line i have only been able to scan it all then display it all in one line in the console but i need to reproduce it line by line

here is the code im using is there a way i can change it do do this? i am very new to c.

the "if f(open) = fail" bit i stole straight out a text book by the way

Code:

---

#include <stdio.h>
#include <unistd.h>

int main(void)
{
  int i;
  FILE *fp;
 
  if ((fp=fopen("datafile", "r")) == NULL)
    {
      fprintf(stderr, "Failed to open file\n");
      exit(1);
    } else
      {
        {
          char input[1000];
          rewind(fp);
do
        { i = fscanf(fp, "%s", input);
          printf("%s\n", input);
        }
while(i !=EOF);

        }
        fclose(fp);
      }
  return 0;
}

---

fgets() will read exactly one line of text from the file at a time. You might want to do a search on this forum for fgets() if you haven't used it before.

thansk for your reply yeh i was looking at fgets thinking that would be good but what i dont understand is where you tell the call what line to read from is it a number? l

i got this call from another thread

Code:

---

char line[80];
 
  if ( fgets( line, sizeof(line),stdin ) != NULL )
  {
      printf("%s...\n",line);
  }

---

where do i tell c what line to access in the file?

You can't. FILE pointers just work with streams. To C, the file just looks like one long line of bytes. However, lines are separated by newlines ('\n') and fgets() picks up on that. So the first call to fgets() after opening the file will read all the characters up until it reaches a '\n' character. The next call to fgets() reads everying after that first '\n' up until it reaches another '\n'. So the file system has no clue what a line is at the level you're talking about. What you can do is use fgets() in a loop. So say you want to read line 5, call fgets() 5 times and then the buffer will hold the 5th line of the file. Does that make sense?

right kinda yeh so if i just modify that code to say

Code:

---

char line[80];
  do
{
  if ( fgets( line, sizeof(line,stdin ) != NULL )
  {
      printf("%s...\n",line);
  }
}
while(i !=EOF);

---

will this loop through the whole file and print each line ive tried it but getting errors
"too few functions to fgets" would this idea work?

wait ive just relised that i does not exist now that the code has bene changed how can i tell it to keep looping until the end of file is reached?

Pair up your parentheses.

Code:

---

if ( fgets( line, sizeof(line,stdin ) != NULL )

---

Try this.

Code:

---

char line[80];
while ( fgets( line, sizeof line, stdin ) != NULL )
{
  printf("%s...\n",line);
}

---

[edit]Before you ask: getting rid of the newline.

hmm nope doesnt seem to be working when i use that code above it just seems to print out "..." every time you hit the return button and goes on for ever

Replace stdin your stream fp.

brilliant thank you guys great job

You seem to have most of the program, but you are having troubles organizing everything. what i would do i

Code:

---

#define  datafile  30

---

that will be the max character length of your filename. Then declare

Code:

---

char  name[datafile];

---

This is just a string to hold the name of the file.
Then i would just use

Code:

---

gets(name);

---

to read the string.
Then to be able to account for an error id use

Code:

---

if ((fp = fopen(name, "r")) == NULL)
        {
                printf("Cannot open %s\n", name);
                exit(1);        /* End execution with  error code */
        }

---

Then to read the file we can use

Code:

---

while((i = getc(fp)) != EOF)
                putchar(i);/*display the numbers*/

---

Then you just close the file after your done with it. Hope this helps

oooooh one last question dont know if this would be possible somehow but could you read 2 lines print them on the cosole in one line then go on to the next two lines print the on the next line of the console if you know what i mean so text file is like

item1
item2
item3
item4
.
.
.

and the cosole will display
item 1 item 2
item 3 item 4

is this possible ?

Code:

---

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

int main(void)
{
  FILE *file = fopen("datafile", "r");
  if ( file )
  {
      char line1[80], line2[80];
      for ( ;; )
      {
        char *newline;
        if ( fgets(line1, sizeof line1, file) == NULL )
        {
            break;
        }
        newline = &line1[strlen(line1) - 1];
        if ( *newline == '\n' )
        {
            *newline = '\0';
        }
        if ( fgets(line2, sizeof line2, file) == NULL )
        {
            break;
        }
        newline = &line2[strlen(line2) - 1];
        if ( *newline == '\n' )
        {
            *newline = '\0';
        }
        printf("%s %s\n", line1, line2);
      }
      fclose(file);
  }
  return 0;
}

/* my output
item1 item2
item3 etc
etc etc
*/

---

hi thanks for that piece of code works a treat just a couple of questions aboutwhat things do

Code:

---

for (;;)

---

what does this do ?

and also

Code:

---

newline = &line1[strlen(line1) - 1];
        if ( *newline == '\n' )
        {
            *newline = '\0';
        }

---

here i have a rough idea but not sure what is actually going on
thanks

Its finding out the length of the line, seeing if it has a carriage return '\n' then replacing it with null '\0'

Quote:

---

Originally Posted by bob56

hi thanks for that piece of code works a treat just a couple of questions aboutwhat things do

Code:

---

for (;;)

---

what does this do ?

---

It is an unconditional loop. Instead the loop is broken within the loop body when one of the input attempts fails.

Quote:

---

Originally Posted by bob56

and also

Code:

---

newline = &line1[strlen(line1) - 1];
        if ( *newline == '\n' )
        {
            *newline = '\0';
        }

---

here i have a rough idea but not sure what is actually going on
thanks

---

It is similar to what is shown in the FAQ, and as already pointed out, it is used to strip the terminating newline character if it is found.