I am very new to C programming. Lets assume that the program creates a number of string separated by lines. Is it possible to fgets() the last line of the file? If yes, then how?
View 2 RepliesI 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??
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;
}
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] ....
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'
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]...
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?
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)
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] ....
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
...
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]...
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.
First of all I need to know how to read from file.
Second, I need to read line by line from the file.
For example, the file contains:
8H 3S TH 9D 5S
5D KD 9H 4D 3D
8C TD 5D QS 2C
I wanna use array, so I need to store 8H in array[0], 3S in array[1], until 5S get stored in array[4].
I need to read the first line, the the second, and then the third.
How can a mulitline string be read line by line
ex: str = "PERIOD="week"
DAY="day"
TIME="time"";
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?
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] ....
I am executing below sample program
Code: #include<iostream.h>
#include <fstream.h>
using namespace std;
int main()
[Code]......
when i am counting the lines using wc command it is giving 1 instead of 2.
I have a problem writing new line in a file. So far, this is my code.
Code:
fprintf(f, (ctime(&mytime)));
fprintf(f, "%s %s %d %d", item, brand, price, amount);
fprintf(f, "
");
fclose(f);
how to read the next line in the file. I think I need to use a for loop, but not sure how to implement it.Lets say my input.txt file has three names:
Sally
Tom
Sugar
I can get Sally, but not tom as yet. fgets also gets me to the same place.
Code:
int main(){
char str_1;
FILE * ifp = fopen("input.txt", "r");
fscanf(ifp, "%s", &str_1);
printf("%s", &str_1);
return 0;
}
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.
Well,i hav a question requiring me to edit sales achieved by an employee for a particular month.
I'm having a dat.file which following format
Employee ID
Name
Sales(for a year)
For example
A00001
Harlem Shake
10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 110.00 120.00
Wad I wanna is TO EDIT only the sales for July which is 70.00 to a new amount with other months remain intact.
I need to search particular id which will then link to their respective sales.
ofstream outFile;
string empID;
cout<<"Please Enter Employee ID:
[Code] ....
I tried to run myself before.But I could only create a new line instead of replacing.
To my understanding with ios::app ..will use the same file for editing..
I'm trying to read in a file specified in the command line but I'm having some trouble. The command line entry specifies the inputfile preceded by '<' and the output file preceded by '>' like so
./program -v < input_file.cmd > output_file.cmd
This is what I've got so far.
int main(int argc,char* argv[]){
string strv="-v";
string input="<";
string output=">";
string str;
string input_file;
const char* in=input_file.c_str();
[Code] .....
This compiles ok, but when i run it using :
./program -v < test1.cmd
I get a segfault, if i cout argc it returns '2' where i would expect for this command line entry, I 'd get 4.
I'm not yet outputting to file, just to the screen so im not specifying an output file yet.
#include <iostream>
#include <string>
#include <fstream>
#include <iomanip>
[Code]....
assume here the list that i output alice wonderland,8563 capitain jack,842 john carpenter,753leisely chow,421 how do i delete "john carpenter, 753" and rearrange my list in the file like alice wonderland,8563 capitain jack,842 leisely chow,421 i have read about remove function, but it only removes the hole file, but i want to keep the file only modify the lists in the file
My file has these lines.I try to remove extra line in the end, in notepad/gedit, however, after saving it automatically adds up there.
one
two
three
Code:
void help::read_ref(const char* file_name){
std::ifstream file_handle;
file_handle.open(file_name);
std::string line,name;
getline(file_handle,line);
while(!file_handle.eof()){
[code]......
when I print size of map, it comes out to be an extra then what is should be.
std::map<std::String,std::string> ->is my map
on the contrary if I use Code: file_handle >> line; I get correct number of entries in map.
My doubt: getline, automatically finds and in last, it finds a , why it doesn't end the iteration?
I have faced this issue many number of times.
Code: line[0]=='>' I am making this check, then also, I get a null string as key in my map.
I have printed key with their index, using Code: map iterator .
How can i display a string per line on the .txt i made? There are 2 .txt files, the one has: John Finn Xach The other is: password1 password2 password3 Question is: How can i display, let's say, i input "John" so it will display something like this "John's password is password1" or if i input Xach, "Xach's password is password3" When i use something like :
Code:
while(getline(passwordFile, str))
{cout<< username <<" password is " << str;
break;
}
It will work for when i input "John", but it doesn't work if I input "Finn" or "Xach"
EDIT: I tried this one:
Code:
while(getline(userFile, str1) && (passwordFile, str2))
{
cout<< str1 <<" password is " << str2;
break;
The output would be: Finn password is password1
It iterates the username but not the password.
I'm making a game that requires the user to enter a correct username and password to play. I have a list of accepted ones saved in a txt file. How do i read each line of the file and check it with the one entered? I know how to use strcmp(string1, string2). I just need to know how to move from one line to the next. This is what I have for this part of the program so far. Also, I think im using the feof() wrong.
Code:
id = fopen("F://CS223/namepass.txt", "r");
score = fopen("F://CS223/scores.txt", "a");
srand(time(NULL));
if(id == NULL)
{
printf("ERROR");
[Code] .....