how to find the integers that are written after a keyword in a file

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I have a file which have the following data

3550: async from 60:159 to 128:0 node 2180 handle 51 size 204:4
3552: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3553: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3554: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3555: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3556: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3557: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3558: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3559: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3560: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3561: call  from 122:122 to 60:0 node 35 handle 9 size 100:4
3562: reply from 60:182 to 122:122 node 0 handle -1 size 4:0
3563: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3564: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3565: async from 60:72 to 124:0 node 571 handle 6 size 300:4
3566: async from 124:124 to 60:0 node 138 handle 1 size 100:4
3567: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3568: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3569: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3570: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3571: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3572: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3573: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3574: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3575: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3576: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3577: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3578: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3579: async from 124:124 to 60:0 node 23 handle 6 size 64:0
3580: call  from 122:122 to 60:0 node 35 handle 9 size 100:4
3581: reply from 60:187 to 122:122 node 0 handle -1 size 4:0
3582: async from 124:124 to 60:0 node 23 handle 6 size 64:0

I want to detect the integers that are written after from .i.e.64,124.
I want Do it in C only.Any help how to do it?

Posted 30-Aug-12 7:40am

Tarun Batra

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JackDingler · Answer 1 · 2012-08-30T07:44:00

Solution 1

Load a line of the file into a character buffer.

Use strstr(szBuffer, "from") to find the pointer to the "from" substring.

Add strlen("from") to the pointer.

This will give you the approximate location of the text you want.

Example - Untested, just banged it out. Some debugging may be required...

C++

#include "stdio.h"

int main ()
{
  FILE * pFile;
  pFile = fopen ("myfile.txt", "r");
  if (pFile==NULL)
     return -1;

  char szBuffer[65536];

  while (fgets(szBuffer, sizeof(szBuffer), pFile))
  {
    char * pFromLoc = strstr(szBuffer, "from");
    if (pFromLoc == NULL)
      continue;

    char *pNumberStart = pFromLoc + strlen("from"); 

    int Number = atoi(pNumberStart);
    printf("%d\n", Number);
  }
    
  fclose (pFile);

  return 0;
}

Posted 30-Aug-12 7:44am

JackDingler

Updated 30-Aug-12 8:24am

v4

Comments

Tarun Batra 30-Aug-12 13:51pm

Any sample code sir...????

enhzflep 30-Aug-12 14:48pm

There's a code sample in Jack's post now. :)

Another (very nasty) approach would start with an assessment that the number in concern starts at the same position on each line - BUT only for the first number after the word 'from' - It would be considered bad/poor practise to extract a number from a point that was 17 bytes after the start of the line.

Removing the search step and replacing it with a simple offset would only be a valid/better solution on systems with little speed and power + other resources. An embedded micro-controller - though these days, it's likely that this approach would provide no benefit.

Tarun Batra 30-Aug-12 15:00pm

Sir can u provide a sample code

enhzflep 30-Aug-12 15:07pm

:confused:
What do you mean my friend?

Jack DID post a sample. You need to adapt it to suit your needs. All you need to do is change the opened file from myfile.txt to whatever your data file is called

Tarun Batra 30-Aug-12 15:10pm

ohk now got your point

enhzflep 30-Aug-12 15:22pm

:)

Tarun Batra 30-Aug-12 15:40pm

Hello sir just tell me one more thing that if i want to return all integers that will come in " int Number" at one instant then how should i do

enhzflep 30-Aug-12 15:48pm

The easiest way would be to use a std::vector of ints.
That way, you don't need to know how many lines there are - each time you read a new number, you simply push_back (put at end of array) the new value.
Here's some more info: std::vector push_back example

EDIT: Missed the "C" tag. If you can use C++, use a vector. If not, just make a quick and simple linked list. Each node only needs to store an int and a pointer to the next node. There's a bazillion posts/articles/tutes on making a linked list.

JackDingler 30-Aug-12 15:51pm

Good answer....

JackDingler 30-Aug-12 15:57pm

Or allocate an array using malloc(sizeof(int) * Count);

enhzflep 30-Aug-12 15:59pm

Oh yeah, of course. Never thought of pre-scanning the file to count the number of lines. (It may even consume fewer cpu cycles than using a vector too) +5

Tarun Batra 30-Aug-12 16:03pm

i can't use c++,i have to do it in C actually in am working in linux(android ndk).

enhzflep 30-Aug-12 15:57pm

Thanks mate - to be fair, it always is easier to go second. (as I did)
You answer gets my +5. :)

JackDingler 30-Aug-12 15:58pm

But you have to know what 'Count' is :)

Tarun Batra 30-Aug-12 16:03pm

i can't use c++,i have to do it in C actually in am working in linux(android ndk).

Tarun Batra 30-Aug-12 16:17pm

sir i have written some solution can u check that and please explain the realloc concept(if possible by pseudo code).

Tarun Batra 30-Aug-12 15:58pm

i can't use c++

Tarun Batra 30-Aug-12 16:23pm

sir i have written some solution can u check that and please explain the realloc concept(if possible by pseudo code).

Tarun Batra 30-Aug-12 15:40pm

Hello sir just tell me one more thing that if i want to return all integers that will come in " int Number" at one instant then how should i do

JackDingler 30-Aug-12 15:46pm

I don't understand your question.

You want to put them into array or something?

Tarun Batra 30-Aug-12 15:49pm

ya how to put them into array as sometimes i have 16 entries in the files sometimes its around 40 and want to return the array

Tarun Batra 30-Aug-12 15:48pm

ya how to put them into array as sometimes i have 16 entries in the files sometimes its around 40 and want to return the array

JackDingler 30-Aug-12 16:03pm

To do it in 'C' with such small counts, the malloc technique works well.

Start with an initial size that seems like it'll work for most cases.
malloc() an array of that size.
Insert your numbers at those indexes.
if you run out of room, call realloc to create a new array.

I will not post an example this time. These important concepts to learn. The answer will sink in better if you research them yourself and write the code yourself.

Tarun Batra 30-Aug-12 16:10pm

sir i have written some solution can u check that and please explain the realloc concept(if possible by pseudo code).

JackDingler 31-Aug-12 11:17am

realloc() takes your existing pointer to memory and attempts to resize it. It will copy your data so it isn't lost, and give you a new pointer to your data.

There is lot's of documentation on the web for this.