Searching text file

Hey guys, I am having some trouble reading a file for a specific string then getting the next two lines of numbers after it. The file would look something like this:

Bill
12345 67890
64528 09342
Jeff
34872 58908
17830 47674
Moose
12465 06854
48736 40985

Say I need to get the numbers after Jeff. How should I do that?
I have already been able to locate the desired string "Jeff".

Thank you for your time.

InicDominus

think of this as looking line by line for a sequence of events. so in these cases you will implement what is called a 'state machine'. if you haven't heard that term don't worry. there are multiple ways to implement such a thing. here is how I like to do it for a simple case like this (pseudocode)

Code:

---

state = 0
while(read a line of text == success)
    switch(state) {
    case 0:
      // looking for 'jeff'
      if line == Jeff
          state = 1;
      break;
    case 1:
      // read the first number
      read number1 from line
      state = 2;
      break;
    case 2:
      // read the second number
      read number2 from line
      state = 3;
      break;
    default:
      // all done, do nothing
      break;
    }
} // end loop or whatever

---

instead of a 'switch' you can use 'if' statements instead. 'if state == 1 do first step, state =2; if state == 2 do second step. state = 3...'

Post the code you use to find "Jeff", and we can give you specific advise. Generally, you have a file pointer that has just passed the 'f' in "Jeff" (fgets takes you up to the newline, fscanf() depends on the format specifiers).

That's why I ask you to post the code you're using to find "Jeff".

Thank you for the fast reply. I will give that a shot.

Sorry about the delayed response. I don't have internet acces on my coding computer so it takes some running around to get here. This is what i use to find the word:

Code:

---

File *file;
file = fopen("/home/user/Desktop/text.txt", "r");
char line[256];
int line_num = 1;
char term[12] = "SATELLITE 1";

if(file != NULL)
{
        while(fgets(line, sizeof(line), file))
        {
                if(strstr(line, term) != NULL)
                {
                        write(output_file, line, sizeof(term));
                }
                    ++line_num;
        }
}

---

Also, I should mention that the actual text I read from wil be thousands of lines long and the special string could be anywhere. The length of all the numbers after it will be the same though. I know this may be a sloppy way of reading the file. I've never used C before this summer.
Thanks again

And I'd like to assign each number to a variable.
ex. num1 = 34872
num2 =58908
num3 = 17830
num4 = 47674

No problem. :cool:

So right after you have confirmed that the target string has been found, (right before or after this line of code: write(output_file, line, sizeof(term));

you need to use code similar to this sort of pseudo code:

Code:

---

  use fgets() inside the if statement confirming you have the target string
  use sscanf(line, "%d %d", &num1, &num2);
  right afterward, to get the first two numbers

  repeat the fgets() and sscanf() just like above
  to get num3 and num4

  process anything you need to do with num1 - num4
  before the end of the if statement

---

Thank you very much this is great!

Well, it looked good and I'm sure it's fine. I am just still having trouble getting to the next two lines after finding the target string. Some debugging I did said that when I used the sscanf(line, "%d %d", &num1, &num2); the num variables were empty. I am assuming that is because I do not know how to tell it to go to the line after the target string?
Sorry for my confusion.

It's a bit tricky. If you try to strcmp(line, targetName), then you will have the problem of fgets() adding in the newline at the end of the line, like it always does if it has room for it.

Which causes the strcmp() to always fail.

Study this:

Code:

---

  while(fgets(line, sizeof(line),fp)) {
      sscanf(line, "%s", name);
     
      if((strcmp(target, name))==0) {
        fgets(line, sizeof(line),fp);
        sscanf(line, "%d %d",&num1, &num2);
        fgets(line, sizeof(line), fp);
        sscanf(line, "%d %d",&num3, &num4);
   
        printf("%s's numbers are %d, %d, %d and %d\n",target,num1,num2,num3,num4);
      }
  }

---

Okay I got this one working. I just replaced that if statement with one I already had [ if(strstr(line, term) != NULL)]
Thank you so much for your time and help!

Quote:

---

Originally Posted by InicDominus

Okay I got this one working. I just replaced that if statement with one I already had [ if(strstr(line, term) != NULL)]
Thank you so much for your time and help!

---

Quite welcome.

Okay, so of course after that works I am told that the data contains doubles and hex numbers so I should just store the whole line as a string. From the code above, I am already at the right line in the file. I am just having trouble saving the whole line as a string. I know sscanf only read until whitespace but I cannot find anything that just gets or copies the whole line to a string.

Quote:

---

Originally Posted by InicDominus

Okay, so of course after that works I am told that the data contains doubles and hex numbers so I should just store the whole line as a string. From the code above, I am already at the right line in the file. I am just having trouble saving the whole line as a string. I know sscanf only read until whitespace but I cannot find anything that just gets or copies the whole line to a string.

---

If I wanted to get a whole string (a row) of text from a file -- ready for this? -- I'd use filegetstring, which we call:

Code:

---

fgets(myCharArrayName, sizeof(myCharArrayName), myfilePointerName);

---

Pretty slick, eh? :cool:

Very slick!
I tried that but I must be missing something /:
That is in the line after the target string?
Would I do the same thing to get the second line of data?
When I try, it doesnt seem to save anything

Post the code you're trying to get working. Crystal ball is in the shop! :)

Code:

---

FILE* output_file;
output_file = fopen("pathToFile", "w");

FILE* file;
file = fopen("pathToFile", "r");

char line[256];
char term[12] = "TARGET";
char data1[256];
char data2[256];

if (file != NULL)
{
    while (fgets(line, sizeof(line), file))
    {
        if (strstr(line,term) != NULL)        //finds TARGET
        {
            fgets(line, sizeof(line), file); 
            fgets(data1, sizeof(data1), file);        //recommended code
            fprintf(output_file, data1, sizeof(data1)); //trying* to write
        }
    }
}

fclose(file);

---

Unfortunately, I have already erased your data file from my computer. Can you post a small example of the data file that is failing with your code?

Your fprintf() line of code should be:

fprintf(output_file, "%s\n", data1);

you have it confused with the format for fgets().

You are getting no warnings or errors from this?

the data i am searching for will look something like this:

TARGET
1 4237568 -24001356 e236484865 1235.438975
2 65.34576 4798722 u394623 .234568 23468769

there is always a main name (TARGET) followed by 2 lines of data labeled 1 and 2. also there are hundreds line sets just like this before and after but all with a different main name.

also for some reason it is no longer printing the target name to the file either. i will go back and see how i messed that up

i was not getting any errors as it was but it is still not working. thank you for fixing my confusion there though!

from recent testing. i am completely unable to write anything to the output file and cannot find how the code i provided earlier prevents that.:frown:

Just used stdout to test and was able to get everything working fine. thanks again for all your help!