fscanf into a 2d array in C
I want to scan elements from a txt into an array. The txt doesnt have how many rows or collumns i'm gonna have, it only contains a cordinate, and the elements of the array. It looks like this:
2,3
2,1
3,0
-
How can i put these numbers into an array so that array[0][0] will be 2 and array[1][0] will be 3 etc...
I want to make this work with other inputs as well.
My code so far :
The ?? is there because I have no idea how i should declare these if i dont even know how many rows or collumns every input txt will have.
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE* in = fopen("in.txt", "r");
int x, y;
int array[??][??];
if (in == NULL) {
printf("Can't open in.txt");
fclose(in);
return 1;
}
if (fscanf(in, "%d,%dn", &x, &y) != 2) {
printf("Cant read file.");
return 2;
}
for (int i = 0; i < ??; i++) {
for (int j = 0; j < ??; j++)
fscanf(in, "%d", &array[i][j]);
}
return 0;
}
c arrays scanf
asked Nov 22 at 18:59
Stan Marsh
216
add a comment |
I want to scan elements from a txt into an array. The txt doesnt have how many rows or collumns i'm gonna have, it only contains a cordinate, and the elements of the array. It looks like this:
2,3
2,1
3,0
-
How can i put these numbers into an array so that array[0][0] will be 2 and array[1][0] will be 3 etc...
I want to make this work with other inputs as well.
My code so far :
The ?? is there because I have no idea how i should declare these if i dont even know how many rows or collumns every input txt will have.
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE* in = fopen("in.txt", "r");
int x, y;
int array[??][??];
if (in == NULL) {
printf("Can't open in.txt");
fclose(in);
return 1;
}
if (fscanf(in, "%d,%dn", &x, &y) != 2) {
printf("Cant read file.");
return 2;
}
for (int i = 0; i < ??; i++) {
for (int j = 0; j < ??; j++)
fscanf(in, "%d", &array[i][j]);
}
return 0;
}
c arrays scanf
asked Nov 22 at 18:59
Stan Marsh
216
You say "it only contains a cordinate, and the elements" but I don't see the coordinate forarray[0][0]in the example input.
– Weather Vane
Nov 22 at 19:02
1
Wouldn't it bearray[0][1]that should be3, andarray[1][0]be the next2? That would make more sense to me.
– Some programmer dude
Nov 22 at 19:06
The question is not clear to me; why do you readxandy? Are they actually the array bounds? But earlier you say you don't know the array bounds. It would improve the question to try and describe this better, as well as provide a realistic example of the file you are trying to read. For the file you provided you just need an array of fixed width 2 , since each row has 2 elements
– M.M
Nov 22 at 21:14
add a comment |
I want to scan elements from a txt into an array. The txt doesnt have how many rows or collumns i'm gonna have, it only contains a cordinate, and the elements of the array. It looks like this:
2,3
2,1
3,0
-
How can i put these numbers into an array so that array[0][0] will be 2 and array[1][0] will be 3 etc...
I want to make this work with other inputs as well.
My code so far :
The ?? is there because I have no idea how i should declare these if i dont even know how many rows or collumns every input txt will have.
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE* in = fopen("in.txt", "r");
int x, y;
int array[??][??];
if (in == NULL) {
printf("Can't open in.txt");
fclose(in);
return 1;
}
if (fscanf(in, "%d,%dn", &x, &y) != 2) {
printf("Cant read file.");
return 2;
}
for (int i = 0; i < ??; i++) {
for (int j = 0; j < ??; j++)
fscanf(in, "%d", &array[i][j]);
}
return 0;
}
c arrays scanf
asked Nov 22 at 18:59
Stan Marsh
216
I want to scan elements from a txt into an array. The txt doesnt have how many rows or collumns i'm gonna have, it only contains a cordinate, and the elements of the array. It looks like this:
2,3
2,1
3,0
-
How can i put these numbers into an array so that array[0][0] will be 2 and array[1][0] will be 3 etc...
I want to make this work with other inputs as well.
My code so far :
The ?? is there because I have no idea how i should declare these if i dont even know how many rows or collumns every input txt will have.
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE* in = fopen("in.txt", "r");
int x, y;
int array[??][??];
if (in == NULL) {
printf("Can't open in.txt");
fclose(in);
return 1;
}
if (fscanf(in, "%d,%dn", &x, &y) != 2) {
printf("Cant read file.");
return 2;
}
for (int i = 0; i < ??; i++) {
for (int j = 0; j < ??; j++)
fscanf(in, "%d", &array[i][j]);
}
return 0;
}
c arrays scanf
c arrays scanf
asked Nov 22 at 18:59
Stan Marsh
216
asked Nov 22 at 18:59
Stan Marsh
216
asked Nov 22 at 18:59
Stan Marsh
216
asked Nov 22 at 18:59
Stan Marsh
216
asked Nov 22 at 18:59
Stan Marsh
216
216
You say "it only contains a cordinate, and the elements" but I don't see the coordinate forarray[0][0]in the example input.
– Weather Vane
Nov 22 at 19:02
1
Wouldn't it bearray[0][1]that should be3, andarray[1][0]be the next2? That would make more sense to me.
– Some programmer dude
Nov 22 at 19:06
The question is not clear to me; why do you readxandy? Are they actually the array bounds? But earlier you say you don't know the array bounds. It would improve the question to try and describe this better, as well as provide a realistic example of the file you are trying to read. For the file you provided you just need an array of fixed width 2 , since each row has 2 elements
– M.M
Nov 22 at 21:14
add a comment |
You say "it only contains a cordinate, and the elements" but I don't see the coordinate forarray[0][0]in the example input.
– Weather Vane
Nov 22 at 19:02
1
Wouldn't it bearray[0][1]that should be3, andarray[1][0]be the next2? That would make more sense to me.
– Some programmer dude
Nov 22 at 19:06
The question is not clear to me; why do you readxandy? Are they actually the array bounds? But earlier you say you don't know the array bounds. It would improve the question to try and describe this better, as well as provide a realistic example of the file you are trying to read. For the file you provided you just need an array of fixed width 2 , since each row has 2 elements
– M.M
Nov 22 at 21:14
You say "it only contains a cordinate, and the elements" but I don't see the coordinate for
array[0][0] in the example input.– Weather Vane
Nov 22 at 19:02
You say "it only contains a cordinate, and the elements" but I don't see the coordinate for
array[0][0] in the example input.– Weather Vane
Nov 22 at 19:02
1
1
Wouldn't it be
array[0][1] that should be 3, and array[1][0] be the next 2? That would make more sense to me.– Some programmer dude
Nov 22 at 19:06
Wouldn't it be
array[0][1] that should be 3, and array[1][0] be the next 2? That would make more sense to me.– Some programmer dude
Nov 22 at 19:06
The question is not clear to me; why do you read
x and y? Are they actually the array bounds? But earlier you say you don't know the array bounds. It would improve the question to try and describe this better, as well as provide a realistic example of the file you are trying to read. For the file you provided you just need an array of fixed width 2 , since each row has 2 elements– M.M
Nov 22 at 21:14
The question is not clear to me; why do you read
x and y? Are they actually the array bounds? But earlier you say you don't know the array bounds. It would improve the question to try and describe this better, as well as provide a realistic example of the file you are trying to read. For the file you provided you just need an array of fixed width 2 , since each row has 2 elements– M.M
Nov 22 at 21:14
add a comment |
2 Answers
2
active
oldest
votes
You want to read in a list of value pairs? That sounds like you will need to have a (possibly long) array of sets of two numbers. Rather than remembering that X is the first and Y is the second, may I suggest setting up a structure to hold the values. Something like this should work:
int main()
{
FILE* in = fopen("lis.csv", "r");
int count=0;
int error=0;
int x, y;
typedef struct {
int x;
int y;
} COORD;
COORD array[999]={0};
if (in == NULL) {
printf("Can't open in.txt");
fclose(in);
return 1;
}
while(!feof(in))
{
if (fscanf(in, "%d,%dn", &x, &y) != 2) {
printf("Cant read file.");
error=1;
break;
}
array[count].x=x;
array[count].y=y;
count++;
}
return error;
}
I did not add anything bright for the error condition and it helps if you do something with the values after reading them in but you get the idea.
answered Nov 22 at 19:13
user1683793
667613
1
Please see Why iswhile ( !feof (file) )always wrong?
– Weather Vane
Nov 22 at 19:45
I was trying to give a hand with the fscanf and where to store the data. If it were me, I would have written it withwhile(fgets(linein,sizeof(linein), in))It just happens that in this case, with GCC on Linux (and cygwin), the EOF test occurs after the last fscanf so this works fine. If the fscanf did not detect the EOF, the test of fscanf and break will avoid storing polluted data.
– user1683793
Nov 22 at 20:06
add a comment |
You should use dynamic array allocation to scan elements from an unknown txt file into an array.
for C++ programmers the best solution is std::vector.
but C programmers should use alternative solutions.
please read this post: (std::vector alternative for C)
answered Nov 22 at 19:25
Roohollah Yeylaghi Ashrafi
1
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
You want to read in a list of value pairs? That sounds like you will need to have a (possibly long) array of sets of two numbers. Rather than remembering that X is the first and Y is the second, may I suggest setting up a structure to hold the values. Something like this should work:
int main()
{
FILE* in = fopen("lis.csv", "r");
int count=0;
int error=0;
int x, y;
typedef struct {
int x;
int y;
} COORD;
COORD array[999]={0};
if (in == NULL) {
printf("Can't open in.txt");
fclose(in);
return 1;
}
while(!feof(in))
{
if (fscanf(in, "%d,%dn", &x, &y) != 2) {
printf("Cant read file.");
error=1;
break;
}
array[count].x=x;
array[count].y=y;
count++;
}
return error;
}
I did not add anything bright for the error condition and it helps if you do something with the values after reading them in but you get the idea.
answered Nov 22 at 19:13
user1683793
667613
1
Please see Why iswhile ( !feof (file) )always wrong?
– Weather Vane
Nov 22 at 19:45
I was trying to give a hand with the fscanf and where to store the data. If it were me, I would have written it withwhile(fgets(linein,sizeof(linein), in))It just happens that in this case, with GCC on Linux (and cygwin), the EOF test occurs after the last fscanf so this works fine. If the fscanf did not detect the EOF, the test of fscanf and break will avoid storing polluted data.
– user1683793
Nov 22 at 20:06
add a comment |
You want to read in a list of value pairs? That sounds like you will need to have a (possibly long) array of sets of two numbers. Rather than remembering that X is the first and Y is the second, may I suggest setting up a structure to hold the values. Something like this should work:
int main()
{
FILE* in = fopen("lis.csv", "r");
int count=0;
int error=0;
int x, y;
typedef struct {
int x;
int y;
} COORD;
COORD array[999]={0};
if (in == NULL) {
printf("Can't open in.txt");
fclose(in);
return 1;
}
while(!feof(in))
{
if (fscanf(in, "%d,%dn", &x, &y) != 2) {
printf("Cant read file.");
error=1;
break;
}
array[count].x=x;
array[count].y=y;
count++;
}
return error;
}
I did not add anything bright for the error condition and it helps if you do something with the values after reading them in but you get the idea.
answered Nov 22 at 19:13
user1683793
667613
1
Please see Why iswhile ( !feof (file) )always wrong?
– Weather Vane
Nov 22 at 19:45
I was trying to give a hand with the fscanf and where to store the data. If it were me, I would have written it withwhile(fgets(linein,sizeof(linein), in))It just happens that in this case, with GCC on Linux (and cygwin), the EOF test occurs after the last fscanf so this works fine. If the fscanf did not detect the EOF, the test of fscanf and break will avoid storing polluted data.
– user1683793
Nov 22 at 20:06
add a comment |
You want to read in a list of value pairs? That sounds like you will need to have a (possibly long) array of sets of two numbers. Rather than remembering that X is the first and Y is the second, may I suggest setting up a structure to hold the values. Something like this should work:
int main()
{
FILE* in = fopen("lis.csv", "r");
int count=0;
int error=0;
int x, y;
typedef struct {
int x;
int y;
} COORD;
COORD array[999]={0};
if (in == NULL) {
printf("Can't open in.txt");
fclose(in);
return 1;
}
while(!feof(in))
{
if (fscanf(in, "%d,%dn", &x, &y) != 2) {
printf("Cant read file.");
error=1;
break;
}
array[count].x=x;
array[count].y=y;
count++;
}
return error;
}
I did not add anything bright for the error condition and it helps if you do something with the values after reading them in but you get the idea.
answered Nov 22 at 19:13
user1683793
667613
You want to read in a list of value pairs? That sounds like you will need to have a (possibly long) array of sets of two numbers. Rather than remembering that X is the first and Y is the second, may I suggest setting up a structure to hold the values. Something like this should work:
int main()
{
FILE* in = fopen("lis.csv", "r");
int count=0;
int error=0;
int x, y;
typedef struct {
int x;
int y;
} COORD;
COORD array[999]={0};
if (in == NULL) {
printf("Can't open in.txt");
fclose(in);
return 1;
}
while(!feof(in))
{
if (fscanf(in, "%d,%dn", &x, &y) != 2) {
printf("Cant read file.");
error=1;
break;
}
array[count].x=x;
array[count].y=y;
count++;
}
return error;
}
I did not add anything bright for the error condition and it helps if you do something with the values after reading them in but you get the idea.
answered Nov 22 at 19:13
user1683793
667613
answered Nov 22 at 19:13
user1683793
667613
answered Nov 22 at 19:13
user1683793
667613
answered Nov 22 at 19:13
user1683793
667613
667613
1
Please see Why iswhile ( !feof (file) )always wrong?
– Weather Vane
Nov 22 at 19:45
I was trying to give a hand with the fscanf and where to store the data. If it were me, I would have written it withwhile(fgets(linein,sizeof(linein), in))It just happens that in this case, with GCC on Linux (and cygwin), the EOF test occurs after the last fscanf so this works fine. If the fscanf did not detect the EOF, the test of fscanf and break will avoid storing polluted data.
– user1683793
Nov 22 at 20:06
add a comment |
1
Please see Why iswhile ( !feof (file) )always wrong?
– Weather Vane
Nov 22 at 19:45
I was trying to give a hand with the fscanf and where to store the data. If it were me, I would have written it withwhile(fgets(linein,sizeof(linein), in))It just happens that in this case, with GCC on Linux (and cygwin), the EOF test occurs after the last fscanf so this works fine. If the fscanf did not detect the EOF, the test of fscanf and break will avoid storing polluted data.
– user1683793
Nov 22 at 20:06
1
1
Please see Why is
while ( !feof (file) ) always wrong?– Weather Vane
Nov 22 at 19:45
Please see Why is
while ( !feof (file) ) always wrong?– Weather Vane
Nov 22 at 19:45
I was trying to give a hand with the fscanf and where to store the data. If it were me, I would have written it with
while(fgets(linein,sizeof(linein), in)) It just happens that in this case, with GCC on Linux (and cygwin), the EOF test occurs after the last fscanf so this works fine. If the fscanf did not detect the EOF, the test of fscanf and break will avoid storing polluted data.– user1683793
Nov 22 at 20:06
I was trying to give a hand with the fscanf and where to store the data. If it were me, I would have written it with
while(fgets(linein,sizeof(linein), in)) It just happens that in this case, with GCC on Linux (and cygwin), the EOF test occurs after the last fscanf so this works fine. If the fscanf did not detect the EOF, the test of fscanf and break will avoid storing polluted data.– user1683793
Nov 22 at 20:06
add a comment |
You should use dynamic array allocation to scan elements from an unknown txt file into an array.
for C++ programmers the best solution is std::vector.
but C programmers should use alternative solutions.
please read this post: (std::vector alternative for C)
answered Nov 22 at 19:25
Roohollah Yeylaghi Ashrafi
1
add a comment |
You should use dynamic array allocation to scan elements from an unknown txt file into an array.
for C++ programmers the best solution is std::vector.
but C programmers should use alternative solutions.
please read this post: (std::vector alternative for C)
answered Nov 22 at 19:25
Roohollah Yeylaghi Ashrafi
1
add a comment |
You should use dynamic array allocation to scan elements from an unknown txt file into an array.
for C++ programmers the best solution is std::vector.
but C programmers should use alternative solutions.
please read this post: (std::vector alternative for C)
answered Nov 22 at 19:25
Roohollah Yeylaghi Ashrafi
1
You should use dynamic array allocation to scan elements from an unknown txt file into an array.
for C++ programmers the best solution is std::vector.
but C programmers should use alternative solutions.
please read this post: (std::vector alternative for C)
answered Nov 22 at 19:25
Roohollah Yeylaghi Ashrafi
1
answered Nov 22 at 19:25
Roohollah Yeylaghi Ashrafi
1
answered Nov 22 at 19:25
Roohollah Yeylaghi Ashrafi
1
answered Nov 22 at 19:25
Roohollah Yeylaghi Ashrafi
1
1
add a comment |
add a comment |
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You say "it only contains a cordinate, and the elements" but I don't see the coordinate for
array[0][0]in the example input.– Weather Vane
Nov 22 at 19:02
1
Wouldn't it be
array[0][1]that should be3, andarray[1][0]be the next2? That would make more sense to me.– Some programmer dude
Nov 22 at 19:06
The question is not clear to me; why do you read
xandy? Are they actually the array bounds? But earlier you say you don't know the array bounds. It would improve the question to try and describe this better, as well as provide a realistic example of the file you are trying to read. For the file you provided you just need an array of fixed width 2 , since each row has 2 elements– M.M
Nov 22 at 21:14