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Scanning a text file for a string
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Join Date: Feb 2007
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ok so im scanning this text file for the string "model=" the problem is, i need to pull the numbers after that string until it reached the end of that line, this is an easy script but for some reason its just not happening. If someone smarter than myself could tell me where the script went wrong that would be awesome. Please don't send me a script completely different, I need it in this format to work with my project. Thanks!
Here is my code
Yes i know, terrible commenting but i couldnt cmment to the right of ecah line, you get the idea. The comments are under the line that they refer to.
I've attached modelset.txt if you want to see (no i cant edit this file)
The actual modelset.txt is 5.3meg so i just sent this as an example
Here is my code
#include <fstream>
#include <iostream>
using namespace std;
int main()
{
ifstream openfile;
//input file
openfile.open("modelset.txt");
//input file
char bigarray[300];
//array that takes value of the whole line being scanned
char thearray[300];
//array that takes value of big array until =="model=" or '\n'
char str;
//character (used in thearray to go through each value of bigarray
ofstream File;
//output file (is created)
File.open("testmodel.txt");
//output file (is created)
while(!openfile.eof())
//while input isnt at the end of the file
{
openfile.getline(bigarray,300);
//set the current line values to bigarray
int i=0;
//used to go through thearray one spot at a time
while (str !='\n' && thearray!="model=")
//set all values of thearray to bigarray until its end of line or "model="
{
thearray[i] = bigarray[i];
i++;
}
i=0;
//set i back to 0 so thearray starts at thearray[0]
if (thearray=="model=")
//see if its =="model="
{
delete [] thearray;
//clear all values of thearray (is this right?)
int testarray=1;
//boolean used so I don't effect the value of thearray
while ( testarray==1 )
//while my boolean is true (redundant but important)
{
openfile.get(str);
//start scanning thearray again (this starts after model=)
thearray[i] = str;
i++;
if (str=='\n');
//set my boolean false if its end of line
{
testarray = 0;
}
}
File << thearray << "\n";
//print thearray (the numbers after "model=") into my output file "File" (testmodel.txt)
}
}
}Yes i know, terrible commenting but i couldnt cmment to the right of ecah line, you get the idea. The comments are under the line that they refer to.
I've attached modelset.txt if you want to see (no i cant edit this file)
The actual modelset.txt is 5.3meg so i just sent this as an example
Last edited by dalton; Feb 18th, 2007 at 2:42 pm.
I think ye' problems start here:
If you were using <string> class objects, you would able to make the != comparison. However, the only way you could make a boolean comparison between a cstring thearray and a string literal "model=" would be to:
1. First, make sure that in your text file, "model=" is followed immediately by a null terminating character '\0' (using escape characters in your .txt file works best when your file is opened in binary mode)
2. Using the <cstring> function strcmp( ), you can make a direct comparison between two character arrays. The function will return 0 if there are no differences between the cstrings.
Example, lets say you called openfile.getline(bigarray,300); Assuming that the first line of the .txt file contains the "model=" string token you are looking for, bigarray would then look like this:
Notice that the delimiting '\n' newline character has been discarded by use of the getline( ) function. Tip: you will probably want the '\n' newline character in this case in order to determine the end of your array. Either add back in the '\n' character yourself, or use get( ) instead of getline( ).
With the null-terminated "model=", we can now pass bigarray into the strcmp( ) function, and it will only access the cstring up until it hits a null termiator. Even though bigarray has a whole bunch of stuff in it, strcmp(bigarray, "model=") would still return 0 indicating that the cstrings are equal.
At this point, you have determined that the line you extracted from your text file is what you are looking for. You can now make the assumption that everything starting at bigarray[7] will contain the numbers.
while (str !='\n' && thearray!="model=")
//set all values of thearray to bigarray until its end of line or "model="
{
thearray[i] = bigarray[i];
i++;
}If you were using <string> class objects, you would able to make the != comparison. However, the only way you could make a boolean comparison between a cstring thearray and a string literal "model=" would be to:
1. First, make sure that in your text file, "model=" is followed immediately by a null terminating character '\0' (using escape characters in your .txt file works best when your file is opened in binary mode)
2. Using the <cstring> function strcmp( ), you can make a direct comparison between two character arrays. The function will return 0 if there are no differences between the cstrings.
Example, lets say you called openfile.getline(bigarray,300); Assuming that the first line of the .txt file contains the "model=" string token you are looking for, bigarray would then look like this:
C++ Syntax (Toggle Plain Text)
[m][o][d][e][l][=][\0][4][9][5][2]
With the null-terminated "model=", we can now pass bigarray into the strcmp( ) function, and it will only access the cstring up until it hits a null termiator. Even though bigarray has a whole bunch of stuff in it, strcmp(bigarray, "model=") would still return 0 indicating that the cstrings are equal.
At this point, you have determined that the line you extracted from your text file is what you are looking for. You can now make the assumption that everything starting at bigarray[7] will contain the numbers.
Last edited by Ancient Dragon; Feb 18th, 2007 at 5:13 pm. Reason: changed last paragraph per poster's request
Since you are using C++ already, why not do something simple like:
Modify this basic framework to suit your needs.
Oh and btw, don't PM people, its rude. If we get time, we will definately help you out.
C++ Syntax (Toggle Plain Text)
// Not tested #include <fstream> #include <string> int main () { using namespace std ; string my_str ; const char search[] = "model=" ; size_t size = strlen (search) ; size_t pos = 0 ; ifstream in ("modelset.txt") ; ofstream out ("output.txt") ; while ( getline(in, my_str).good () ) { if ( (pos = my_str.find (search, 0)) != string::npos ) { my_str = my_str.erase (pos, size) ; out << atoi (my_str.c_str()) << '\n'; } } // close the file streams in.close () ; out.close () ; getchar ( ) ; return 0 ; }
Modify this basic framework to suit your needs.
Oh and btw, don't PM people, its rude. If we get time, we will definately help you out.
Last edited by ~s.o.s~; Feb 18th, 2007 at 4:12 pm.
I don't accept change; I don't deserve to live.
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Nindon Mein Jo Aaye Jise To Bhul Jaaye Khawab Woh Sachcha Nahi.
Khwaab Ko Raag De, Nind Ko Aag De
Jo Tujhe Jagaaye, Nindein Teri Udaaye Khwaab Hai Sachcha Wahi.
Nindon Mein Jo Aaye Jise To Bhul Jaaye Khawab Woh Sachcha Nahi.
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>Since you are using C++ already, why not do something simple like:
Prolly because his school wants him/her to use and get to know char[] arrays.
>out << atoi (my_str.c_str()) << '\n';
Don't use atoi with c++ or even c for that matter. It is best avoided. Use stringstream instead.
http://www.daniweb.com/techtalkforums/thread39691.html
Oh and I just noticed an EOF in the OPs code which in most circumstances is best avoided.
Prolly because his school wants him/her to use and get to know char[] arrays.
>out << atoi (my_str.c_str()) << '\n';
Don't use atoi with c++ or even c for that matter. It is best avoided. Use stringstream instead.
http://www.daniweb.com/techtalkforums/thread39691.html
Oh and I just noticed an EOF in the OPs code which in most circumstances is best avoided.
Last edited by iamthwee; Feb 18th, 2007 at 4:34 pm.
*Voted best profile in the world*
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>out << atoi (my_str.c_str()) << '\n';
Don't use atoi with c++ or even c for that matter. It is best avoided. Use stringstream instead.
And btw atoi is not always bad, depends on the context which it is used. See this snippet.
Last edited by ~s.o.s~; Feb 18th, 2007 at 10:20 pm.
I don't accept change; I don't deserve to live.
Jo Tujhe Jagaaye, Nindein Teri Udaaye Khwaab Hai Sachcha Wahi.
Nindon Mein Jo Aaye Jise To Bhul Jaaye Khawab Woh Sachcha Nahi.
Khwaab Ko Raag De, Nind Ko Aag De
Jo Tujhe Jagaaye, Nindein Teri Udaaye Khwaab Hai Sachcha Wahi.
Nindon Mein Jo Aaye Jise To Bhul Jaaye Khawab Woh Sachcha Nahi.
Khwaab Ko Raag De, Nind Ko Aag De
I followed your link because now I'm intrigued about atoi, however is for C++ and I don't know anything about it. Do you have another link that shows why is bad to use that function in C. I have used it several times, in the past, following books examples.
"If it moves, tax it. If it keeps moving, regulate it, and if it stops moving, subsidize it" - Ronald Reagan
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I followed your link because now I'm intrigued about atoi, however is for C++ and I don't know anything about it. Do you have another link that shows why is bad to use that function in C. I have used it several times, in the past, following books examples.
http://www.daniweb.com/techtalkforum...tml#post191438
Another way in C for conversion is to validate the string with
strcspn and then use sscanf to retrieve it (although that would be kind of pointless; better to use strtol). "Technological progress is like an axe in the hands of a pathological criminal."
All my posts may be freely redistributed under the terms of the MIT license.
All my posts may be freely redistributed under the terms of the MIT license.
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I followed your link because now I'm intrigued about atoi, however is for C++ and I don't know anything about it. Do you have another link that shows why is bad to use that function in C. I have used it several times, in the past, following books examples.
atoi in that snippet was relatively safe since the string is only to passed to atoi if it contains only digits and nothing else (I make this sure in the if condition). So the chances of junk gettting to passed to atoi are none and hence it functions properly in the given context.I could have used stringstreams but would have been an overkill considering that I know before hand the kind of input which would be passed to the atoi. An important part of being a programmer is the proper selection of tools suiting the situation under consideration.
Last edited by ~s.o.s~; Feb 19th, 2007 at 11:39 am.
I don't accept change; I don't deserve to live.
Jo Tujhe Jagaaye, Nindein Teri Udaaye Khwaab Hai Sachcha Wahi.
Nindon Mein Jo Aaye Jise To Bhul Jaaye Khawab Woh Sachcha Nahi.
Khwaab Ko Raag De, Nind Ko Aag De
Jo Tujhe Jagaaye, Nindein Teri Udaaye Khwaab Hai Sachcha Wahi.
Nindon Mein Jo Aaye Jise To Bhul Jaaye Khawab Woh Sachcha Nahi.
Khwaab Ko Raag De, Nind Ko Aag De
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