C++ :: How To Read Data From A File Line By Line
Jul 2, 2013
I have an external file with one column of data. If I have a counter value let say counter =1, and counter++ and so on. How I can write such a c++ code that if the value of counter and value from the external file are same then generate an action let say cout both values i.e. value of counter and value from external file.
for more information, here is an example:
data in file(in one column): 2 6 8 9 10...
value of counter : 1 2 3 4 5 6 7 8 9...
then cout values only if value of counter and value from the file is same.
Here is my code so far, but it does not seem to work;
#include<iostream>
#include<fstream>
using namespace std;
int main() {
const int SIZE = 10; //Size declaration of array
int hours[SIZE]; //Array declaration
[Code]...
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Jun 27, 2014
I'm reading strings one after another and trying to split it using strtok_r. This doesnot seem to be working
I have a .gz file from which I'm reading the data into the buffer in chunks.
The below code works fine only for the first chunk on data. Later it just breaks out.
while(1) {
char buffer[SIZE];
int bytes_read = gzread (f, buffer, SIZE - 1);
[Code] .....
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Jul 5, 2013
I have a text file (test.txt) with the following data:
01,05,25,20130728
01,06,25,20130728
01,07,25,20130728
01,08,25,20130728
01,05,25,20130728
01,05,25,20130728
01,05,45,20130728
01,05,65,20130728
01,05,85,20130728
01,05,35,20130728
01,05,25,20130728
01,05,35,20130728
I want to read this to one string called line. So far I have this code:
string line;
ifstream myfile ("/home/Test.txt");
if (myfile.is_open()) {
while (myfile.good()) {
getline (myfile, line);
for (int a = 0; a <= 335; a++) {
cout <<line.at(a);
} }
myfile.close();
}
so far its only printing the first line and then throwing an instance of 'std::out_of_range'
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Oct 5, 2013
I need to read a text file which has various lines containing integers. I need to write those integers separately in a vector. Example, the first line of the text file contains 3 9 8 7 6 so vector[4]=3, vector[3]=9, vector[2]=8 and so on. Next read the second line 4 1 2 3 4 5 and write to another vector vector[5]=4, vector[4]=1...
I tried the code below but it will write from the second line, the whole line in one vector index.
int str; // Temp string to
cout << "Read from a file!" << endl;
ifstream fin("functions.txt"); // Open it up!
string line;
// read line count from file; assuming it's the first line
getline( fin, line );
[Code]...
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Jul 23, 2012
How to read a line with maximum of 8 bytes from a line in a file.
Let say line has 10248 bytes in one single line and same repeats for remaining lines in the file.
I need to read the first 8 bytes of a line and go on read the last 2 bytes of the line and repeat the till end of file.
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Jan 23, 2015
I am reading my file (20GB) line by line using boost like this
PHP Code:
boost::interprocess::file_mapping* fm = new boost::interprocess::file_mapping("E:Mountain.7z", boost::interprocess::read_only);
boost::interprocess::mapped_region* mr = new boost::interprocess::mapped_region(*fm, boost::interprocess::read_only);
char* bytes = static_cast<char*>(mr->get_address());
An exception is thrown in the second line while allocating memory for mr.
I use boost because it can also work in Mac which my code will be ported to.
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Mar 7, 2014
How can a mulitline string be read line by line
ex: str = "PERIOD="week"
DAY="day"
TIME="time"";
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Nov 5, 2014
I'm using fgets which will read a single line at a time, but unlike fgets I don't want it to return the new line char ( ) ?I want to be able to use printf to display the lines next to each other.
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Aug 14, 2014
How can I read this file in to my struct?
12345Joe Lim KH879.00
12233Kay Suet Yee35.98
23781Leong Jing Yang 10.00
67543Woon Tian Yi500.50
struct master {
unsigned short int IDnum;
[code]....
not working
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Aug 17, 2014
I am trying to read a file line by line and then do something with the informations, so my method looks like this:
Code:
void open_file(char *link) {
FILE *file = fopen(link, "r");
if (file == NULL) {
fprintf(stderr, "Could not open file.
");
exit(EXIT_FAILURE);
[Code] ....
1) The first complain of valgrind is at the line where I use fgets and its telling me (invalid write of size x), but I have allocated my line to 56000 and the read line is shorter, why is there a write size error then :S?
2) at the line where I realloc where I try to shrink the space he's telling me: Address .... is 0 bytes inside a block of size 56000, But I know i need only this space so why is there a write over space error :S??
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Sep 25, 2013
So I'm reading a file line by line and storing it backwards into a list. So if the file has has this format...
1
2
3
4
The code should store each line in a list as such...
4, 3, 2 ,1
Instead the code will store the last variable in all nodes. So the final list will look like this...
4, 4, 4, 4
Here is my code...
struct node *head = NULL;
int i;
while(read(in, &i, sizeof(int)) != 0) {
struct node *temp = malloc(sizeof(*temp));
temp->line = &i;
temp->next = head;
head = temp;
}
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Jul 15, 2013
I need to read lines from one file and copy them line by line into another file using dynamic memory allocation. It compiles but gives me a seg fault. Why/How?
Code:
int main(){
FILE *fp1;
FILE *fp2;
FILE *i;
fp1=fopen("file1","r");
fp2=fopen("file3","w+");
[Code] ....
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Nov 19, 2013
How do i read the end of the line in a txt or dat file? I treid using fscanf in a while loop like this
Code:
while(fscanf(pfile,"%c") != EOF && fscanf(pfile,"%c") != '') {
char c = ' ';
fscanf(pfile,"%c",&c);
str += c;
}
The reason why its important to stop after each line is that i need the program to read the data from each line separately.
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Apr 12, 2015
Im trying to read from a file, line by line, with no specified number of values in the file. Check out my code:
int main() {
string x;
ifstream fin;
int count = 0;
char ch;
fin.open("CWC_Master.txt");
if(!fin)
[Code] .....
Now, this works great! However, its skipping some lines. And I dont know why. For example: Lets say that the input file is:
superman toy
sm2335
19.99
batman toy
bm5532
25.99
aquaman toy
am6786
26.00
Where it should output the above, instead it outputs every other one. Like:
superman toy
19.99
batman toy
25.99
aquaman toy
26.00
How can I fix my code so that it SIMPLY(i say simply because I am still a beginner coder) can read line by line?
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Aug 24, 2013
I can able to get the last line ten chars but i cant get if the last line is null.
here is my code
#include <cstdlib>
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
using namespace std;
int main(int argc, char *argv[]) {
[Code] ....
here with i have enclosed my file where i am pick my last ten chars ...
Attached Files : log.txt (4.8 KB)
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May 12, 2014
I have to read the information about logic gates from a file. The file format is shown below:
Code:
gateOne = NAND(inpA, inpB)
gate2=NAND(1,2)
3 = NAND(23,25,26)
As, it can be seen from the above structure that whitespaces are not same everytime. So, to deal with this situation, i am using boost library to remove all whitespaces from the line which is being read and then try to find the name of gate and its input. My code is given below which is able to correctly find the gate names and its first input...but my code is not able to find the second, third and so on input names.
Code:
//C
#include <stdio.h>
//C++
#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <cstring>
#include <boost/algorithm/string/erase.hpp>
[Code] ....
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Dec 2, 2013
I have been working on a program to scanfile and whenever it encounters what the user wanted it prints it, and it is all right less the first line of the file that the program jumps,
Code:
#include<stdio.h>#include<string.h>
#include<stdlib.h>
void main()
{
unsigned int j=0 ;
char num[100] , str1[100], str2[100];
FILE *fp;
[Code]....
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Aug 16, 2013
I am making a script to read the latest from a text file. It picks up the line by numbytes in fseek, but the data line may vary and numbytes not be accurate, how can I fix this?
And another problem is that the line has, date, time, value, separated by space, how to read that line and put these 3 information in variable?
#include <stdio.h>
#include <conio.h>
int main() {
FILE *arq;
char Line[100];
char *result;
int tam, i;
// Opens a file for READING TEXT
arq = fopen("temp.txt", "rt");
[code].....
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Oct 3, 2013
I want to read a binary file using as line separator "ff77" in order to parse further each line one by one with some regex since the file is big. I have a small ruby code shown below, but I'm new in C++, and I don't know how to replicate in C++ what this ruby code does.
Code:
#!/usr/bin/env ruby
BEGIN{ $/="xffx77" } # Line separator = FF77
File.open(ARGV[0],"rb") # Open in binary mode
[Code].....
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Nov 2, 2013
I run with debugger and appear this file referring the error to line 142 (in red):
Code:
/***
*xtoa.c - convert integers/longs to ASCII string
*
* The module has code to convert integers/longs to ASCII strings. See
*
*******************************************************************************/
#include <cruntime.h>
#include <stdlib.h>
#include <limits.h>
#include <tchar.h>
#include <internal.h>
#include <internal_securecrt.h>
#ifdef _UNICODE
#define xtox_s xtow_s
[Code] ...
In the calls stack window appears this
Code:
=>msvcr110d.dll!xtoa_s(unsigned long val, char * buf, unsigned int sizeInTChars, unsigned int radix, int is_neg) Line 142C
msvcr110d.dll!_itoa_s(int val, char * buf, unsigned int sizeInTChars, int radix) Line 176C
Get_Blocks.exe!main(int argc, char * * argv) Line 224C++
Get_Blocks.exe!__tmainCRTStartup() Line 536C
Get_Blocks.exe!mainCRTStartup() Line 377C
kernel32.dll!7695336a()Unknown
[Frames below may be incorrect and/or missing, no symbols loaded for kernel32.dll]
ntdll.dll!76f19f72()Unknown
ntdll.dll!76f19f45()Unknown
It seems could be becuase to _itoa_s(), I'm using like this:
Code:
_itoa_s(CONVDEC(i), num, 10, 10);
sub += num;
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Oct 13, 2014
How to read a file line by line and then later access them by doing something like
Code:
lines[0] //Line number one
...
lines[100] //Line number one hundred and one
lines[100][0] //L
lines[100][1] //i
lines[100][2] //n
lines[100][3] //e
lines[100][4] //
lines[100][5] //n
...
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Jun 6, 2013
I build this function in my C++ code. I run the on a UNIX box, build HTML file to use in Windows.
In HTML file building code, I have only a string variable hold the contents of this text file (from unix) & add it into HTML file.
The issue is that when I view the HTML file on windows, it shows all the lines in the text file as one line. I think it lost the CRLF.
My question is when I add lines from text file (reading one line at a time) in UNIX, how do I maintain CRLF ( ) in the stringstream variable so that it will display on HTML in Windows properly, all the lines as it is in unix.
I am aware UNIX uses for line end.
string TextFileToString(string filename) {
string line;
stringstream dosString;
ifstream inFile;
[Code] ......
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May 21, 2012
When I read a text file. I'm reading a list of strings in text file, with one string per line. The first line has extra characters in the string, the rest of the lines read are fine, and I can't understand where the extra characters come from. The file format is this...
A
AA
AAN
AAP
AAPL
AAWW
AAXJ
....
...
Code:
std::vector<std::string> strSymbolList;
std::string s = "";
std::ifstream infile( m_strFileSymbols );
while( std::getline(infile, s) ) {
strSymbolList.push_back(s);
}
infile.close();
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Apr 25, 2013
I have written the following code but i am stuck. Write a program that will prompt the user for a file name and open that file for reading. Print out all the information in the file, numbering each new line of text.
Code:
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <ctype.h>
int main()
{
char line[81], filename[21], c;
int i = 1;
FILE *inFile;
[code]....
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Jun 11, 2014
I have a .txt file which I want to read from and then write a new text file, this time with sorted lines. It is easy to sort one value, but what about sorting entire lines based on one value?
I want to sort the lines based on the FIRST value.
Example text file contents:
values;data
5.01 100
2.9 342
2.69 43534
10.1 43
6.8 45324
Output: Text file containing
2.69 43534
2.9 342
5.01 100
6.8 45324
10.1 43
It's easy to do this if there was only 1 number on each line, but I do I sort all the lines based on the first number in each line?
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May 3, 2013
I wrote the below code to find the line with "abc" as my parameter to strTosearch. I expected to the line 1st line but, this function always match the 2nd line. What am I missing here?
I wanted "found" to be "abc def hgi SSS".
Code in main()
String found=GetstringColSamLine("mytext.txt", "abc");
File name - mytext.txt
abc def hgi SSS
abc ppp yyy
string GetstringColSamLine(string routerFileName, string strTosearch)
[Code] ....
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