How can I delete a line from a text file in C++?
up vote
1
down vote
favorite
I want to delete a line of my text file without replacing it with " ".
Just as a side note: my file has newlines. So I have more than one line (like a table)
void Data::delete_line(const string& idNr) {
ifstream list;
string readFile, id;
list.open("list.txt", ios::app);
if (list.is_open()) {
while (getline(list, readFile)) {
int pos = readFile.find(';');
id = readFile.substr(0, pos);
if (idNr == id) {
//deleting the line here
}
}
}
}
I found this question but it does not solve my problem:
c++ filestream
asked Nov 19 at 19:48
IT_Geek_Oz
209218
|
show 5 more comments
up vote
1
down vote
favorite
I want to delete a line of my text file without replacing it with " ".
Just as a side note: my file has newlines. So I have more than one line (like a table)
void Data::delete_line(const string& idNr) {
ifstream list;
string readFile, id;
list.open("list.txt", ios::app);
if (list.is_open()) {
while (getline(list, readFile)) {
int pos = readFile.find(';');
id = readFile.substr(0, pos);
if (idNr == id) {
//deleting the line here
}
}
}
}
I found this question but it does not solve my problem:
c++ filestream
asked Nov 19 at 19:48
IT_Geek_Oz
209218
4
You can't delete a line from anifstream, at least you'll need to use astd::fstreamwhich is capable to write back to the opened file.
– πάντα ῥεῖ
Nov 19 at 19:52
1
Think of a file like an array. You can't remove the middle element. You have to move everything forward.
– NathanOliver
Nov 19 at 19:53
Everything after that has to move up, so there is no advantage to not creating a new file
– stark
Nov 19 at 19:53
@NathanOliver Thats what I want :) IThe other lines have to move after deleting one line
– IT_Geek_Oz
Nov 19 at 19:53
1
If you need a database, use a database, not a plain file.
– n.m.
Nov 19 at 19:58
|
show 5 more comments
up vote
1
down vote
favorite
up vote
1
down vote
favorite
I want to delete a line of my text file without replacing it with " ".
Just as a side note: my file has newlines. So I have more than one line (like a table)
void Data::delete_line(const string& idNr) {
ifstream list;
string readFile, id;
list.open("list.txt", ios::app);
if (list.is_open()) {
while (getline(list, readFile)) {
int pos = readFile.find(';');
id = readFile.substr(0, pos);
if (idNr == id) {
//deleting the line here
}
}
}
}
I found this question but it does not solve my problem:
c++ filestream
asked Nov 19 at 19:48
IT_Geek_Oz
209218
I want to delete a line of my text file without replacing it with " ".
Just as a side note: my file has newlines. So I have more than one line (like a table)
void Data::delete_line(const string& idNr) {
ifstream list;
string readFile, id;
list.open("list.txt", ios::app);
if (list.is_open()) {
while (getline(list, readFile)) {
int pos = readFile.find(';');
id = readFile.substr(0, pos);
if (idNr == id) {
//deleting the line here
}
}
}
}
I found this question but it does not solve my problem:
c++ filestream
c++ filestream
asked Nov 19 at 19:48
IT_Geek_Oz
209218
asked Nov 19 at 19:48
IT_Geek_Oz
209218
edited Nov 19 at 20:26
asked Nov 19 at 19:48
IT_Geek_Oz
209218
asked Nov 19 at 19:48
IT_Geek_Oz
209218
asked Nov 19 at 19:48
IT_Geek_Oz
209218
209218
4
You can't delete a line from anifstream, at least you'll need to use astd::fstreamwhich is capable to write back to the opened file.
– πάντα ῥεῖ
Nov 19 at 19:52
1
Think of a file like an array. You can't remove the middle element. You have to move everything forward.
– NathanOliver
Nov 19 at 19:53
Everything after that has to move up, so there is no advantage to not creating a new file
– stark
Nov 19 at 19:53
@NathanOliver Thats what I want :) IThe other lines have to move after deleting one line
– IT_Geek_Oz
Nov 19 at 19:53
1
If you need a database, use a database, not a plain file.
– n.m.
Nov 19 at 19:58
|
show 5 more comments
4
You can't delete a line from anifstream, at least you'll need to use astd::fstreamwhich is capable to write back to the opened file.
– πάντα ῥεῖ
Nov 19 at 19:52
1
Think of a file like an array. You can't remove the middle element. You have to move everything forward.
– NathanOliver
Nov 19 at 19:53
Everything after that has to move up, so there is no advantage to not creating a new file
– stark
Nov 19 at 19:53
@NathanOliver Thats what I want :) IThe other lines have to move after deleting one line
– IT_Geek_Oz
Nov 19 at 19:53
1
If you need a database, use a database, not a plain file.
– n.m.
Nov 19 at 19:58
4
4
You can't delete a line from an
ifstream, at least you'll need to use a std::fstream which is capable to write back to the opened file.– πάντα ῥεῖ
Nov 19 at 19:52
You can't delete a line from an
ifstream, at least you'll need to use a std::fstream which is capable to write back to the opened file.– πάντα ῥεῖ
Nov 19 at 19:52
1
1
Think of a file like an array. You can't remove the middle element. You have to move everything forward.
– NathanOliver
Nov 19 at 19:53
Think of a file like an array. You can't remove the middle element. You have to move everything forward.
– NathanOliver
Nov 19 at 19:53
Everything after that has to move up, so there is no advantage to not creating a new file
– stark
Nov 19 at 19:53
Everything after that has to move up, so there is no advantage to not creating a new file
– stark
Nov 19 at 19:53
@NathanOliver Thats what I want :) IThe other lines have to move after deleting one line
– IT_Geek_Oz
Nov 19 at 19:53
@NathanOliver Thats what I want :) IThe other lines have to move after deleting one line
– IT_Geek_Oz
Nov 19 at 19:53
1
1
If you need a database, use a database, not a plain file.
– n.m.
Nov 19 at 19:58
If you need a database, use a database, not a plain file.
– n.m.
Nov 19 at 19:58
|
show 5 more comments
2 Answers
2
active
oldest
votes
up vote
1
down vote
accepted
Maybe you can just create a new file and put your data into the new file. Like this:
void Data::delete_line(const string& idNr) {
ifstream list;
ofstream outFile("newList.txt");
string readFile, id;
list.open("list.txt", ios::app);
if (list.is_open()) {
while (getline(list, readFile)) {
int pos = readFile.find(';');
id = readFile.substr(0, pos);
if (idNr != id) {
outFile << readFile;
}
}
}
list.close();
outFile.close();
remove("list.txt");
rename("newList.txt", "list.txt");
}
At the end you just remove your old file and rename the new file with the name of the old file. I hope this will solve your problem.
answered Nov 19 at 20:34
gmz
395
add a comment |
up vote
0
down vote
Without creating a new file, Its impossible to remove a line in the middle of file. Unless you replace it in place.
So in this state, just you have to use of bellow method :
std::ostream::seekp
Notice this example :
// position in output stream
#include <fstream> // std::ofstream
int main () {
std::ofstream outfile;
outfile.open ("test.txt");
outfile.write ("This is an apple",16);
long pos = outfile.tellp();
outfile.seekp (pos-7);
outfile.write (" sam",4);
outfile.close();
return 0;
}
In this example, tellp is used to get the position in the stream after the writing operation. The pointer is then moved back 7 characters to modify the file at that position, so the final content of the file is:
This is a sample
answered Nov 19 at 20:08
Mohammadreza Panahi
2,52221432
The sample is not working
– IT_Geek_Oz
Nov 19 at 20:17
@MartinYork Fixed...
– Mohammadreza Panahi
Nov 19 at 20:32
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
up vote
1
down vote
accepted
Maybe you can just create a new file and put your data into the new file. Like this:
void Data::delete_line(const string& idNr) {
ifstream list;
ofstream outFile("newList.txt");
string readFile, id;
list.open("list.txt", ios::app);
if (list.is_open()) {
while (getline(list, readFile)) {
int pos = readFile.find(';');
id = readFile.substr(0, pos);
if (idNr != id) {
outFile << readFile;
}
}
}
list.close();
outFile.close();
remove("list.txt");
rename("newList.txt", "list.txt");
}
At the end you just remove your old file and rename the new file with the name of the old file. I hope this will solve your problem.
answered Nov 19 at 20:34
gmz
395
add a comment |
up vote
1
down vote
accepted
Maybe you can just create a new file and put your data into the new file. Like this:
void Data::delete_line(const string& idNr) {
ifstream list;
ofstream outFile("newList.txt");
string readFile, id;
list.open("list.txt", ios::app);
if (list.is_open()) {
while (getline(list, readFile)) {
int pos = readFile.find(';');
id = readFile.substr(0, pos);
if (idNr != id) {
outFile << readFile;
}
}
}
list.close();
outFile.close();
remove("list.txt");
rename("newList.txt", "list.txt");
}
At the end you just remove your old file and rename the new file with the name of the old file. I hope this will solve your problem.
answered Nov 19 at 20:34
gmz
395
add a comment |
up vote
1
down vote
accepted
up vote
1
down vote
accepted
Maybe you can just create a new file and put your data into the new file. Like this:
void Data::delete_line(const string& idNr) {
ifstream list;
ofstream outFile("newList.txt");
string readFile, id;
list.open("list.txt", ios::app);
if (list.is_open()) {
while (getline(list, readFile)) {
int pos = readFile.find(';');
id = readFile.substr(0, pos);
if (idNr != id) {
outFile << readFile;
}
}
}
list.close();
outFile.close();
remove("list.txt");
rename("newList.txt", "list.txt");
}
At the end you just remove your old file and rename the new file with the name of the old file. I hope this will solve your problem.
answered Nov 19 at 20:34
gmz
395
Maybe you can just create a new file and put your data into the new file. Like this:
void Data::delete_line(const string& idNr) {
ifstream list;
ofstream outFile("newList.txt");
string readFile, id;
list.open("list.txt", ios::app);
if (list.is_open()) {
while (getline(list, readFile)) {
int pos = readFile.find(';');
id = readFile.substr(0, pos);
if (idNr != id) {
outFile << readFile;
}
}
}
list.close();
outFile.close();
remove("list.txt");
rename("newList.txt", "list.txt");
}
At the end you just remove your old file and rename the new file with the name of the old file. I hope this will solve your problem.
answered Nov 19 at 20:34
gmz
395
answered Nov 19 at 20:34
gmz
395
answered Nov 19 at 20:34
gmz
395
answered Nov 19 at 20:34
gmz
395
395
add a comment |
add a comment |
up vote
0
down vote
Without creating a new file, Its impossible to remove a line in the middle of file. Unless you replace it in place.
So in this state, just you have to use of bellow method :
std::ostream::seekp
Notice this example :
// position in output stream
#include <fstream> // std::ofstream
int main () {
std::ofstream outfile;
outfile.open ("test.txt");
outfile.write ("This is an apple",16);
long pos = outfile.tellp();
outfile.seekp (pos-7);
outfile.write (" sam",4);
outfile.close();
return 0;
}
In this example, tellp is used to get the position in the stream after the writing operation. The pointer is then moved back 7 characters to modify the file at that position, so the final content of the file is:
This is a sample
answered Nov 19 at 20:08
Mohammadreza Panahi
2,52221432
The sample is not working
– IT_Geek_Oz
Nov 19 at 20:17
@MartinYork Fixed...
– Mohammadreza Panahi
Nov 19 at 20:32
add a comment |
up vote
0
down vote
Without creating a new file, Its impossible to remove a line in the middle of file. Unless you replace it in place.
So in this state, just you have to use of bellow method :
std::ostream::seekp
Notice this example :
// position in output stream
#include <fstream> // std::ofstream
int main () {
std::ofstream outfile;
outfile.open ("test.txt");
outfile.write ("This is an apple",16);
long pos = outfile.tellp();
outfile.seekp (pos-7);
outfile.write (" sam",4);
outfile.close();
return 0;
}
In this example, tellp is used to get the position in the stream after the writing operation. The pointer is then moved back 7 characters to modify the file at that position, so the final content of the file is:
This is a sample
answered Nov 19 at 20:08
Mohammadreza Panahi
2,52221432
The sample is not working
– IT_Geek_Oz
Nov 19 at 20:17
@MartinYork Fixed...
– Mohammadreza Panahi
Nov 19 at 20:32
add a comment |
up vote
0
down vote
up vote
0
down vote
Without creating a new file, Its impossible to remove a line in the middle of file. Unless you replace it in place.
So in this state, just you have to use of bellow method :
std::ostream::seekp
Notice this example :
// position in output stream
#include <fstream> // std::ofstream
int main () {
std::ofstream outfile;
outfile.open ("test.txt");
outfile.write ("This is an apple",16);
long pos = outfile.tellp();
outfile.seekp (pos-7);
outfile.write (" sam",4);
outfile.close();
return 0;
}
In this example, tellp is used to get the position in the stream after the writing operation. The pointer is then moved back 7 characters to modify the file at that position, so the final content of the file is:
This is a sample
answered Nov 19 at 20:08
Mohammadreza Panahi
2,52221432
Without creating a new file, Its impossible to remove a line in the middle of file. Unless you replace it in place.
So in this state, just you have to use of bellow method :
std::ostream::seekp
Notice this example :
// position in output stream
#include <fstream> // std::ofstream
int main () {
std::ofstream outfile;
outfile.open ("test.txt");
outfile.write ("This is an apple",16);
long pos = outfile.tellp();
outfile.seekp (pos-7);
outfile.write (" sam",4);
outfile.close();
return 0;
}
In this example, tellp is used to get the position in the stream after the writing operation. The pointer is then moved back 7 characters to modify the file at that position, so the final content of the file is:
This is a sample
answered Nov 19 at 20:08
Mohammadreza Panahi
2,52221432
edited Nov 19 at 20:32
answered Nov 19 at 20:08
Mohammadreza Panahi
2,52221432
answered Nov 19 at 20:08
Mohammadreza Panahi
2,52221432
answered Nov 19 at 20:08
Mohammadreza Panahi
2,52221432
2,52221432
The sample is not working
– IT_Geek_Oz
Nov 19 at 20:17
@MartinYork Fixed...
– Mohammadreza Panahi
Nov 19 at 20:32
add a comment |
The sample is not working
– IT_Geek_Oz
Nov 19 at 20:17
@MartinYork Fixed...
– Mohammadreza Panahi
Nov 19 at 20:32
The sample is not working
– IT_Geek_Oz
Nov 19 at 20:17
The sample is not working
– IT_Geek_Oz
Nov 19 at 20:17
@MartinYork Fixed...
– Mohammadreza Panahi
Nov 19 at 20:32
@MartinYork Fixed...
– Mohammadreza Panahi
Nov 19 at 20:32
add a comment |
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4
You can't delete a line from an
ifstream, at least you'll need to use astd::fstreamwhich is capable to write back to the opened file.– πάντα ῥεῖ
Nov 19 at 19:52
1
Think of a file like an array. You can't remove the middle element. You have to move everything forward.
– NathanOliver
Nov 19 at 19:53
Everything after that has to move up, so there is no advantage to not creating a new file
– stark
Nov 19 at 19:53
@NathanOliver Thats what I want :) IThe other lines have to move after deleting one line
– IT_Geek_Oz
Nov 19 at 19:53
1
If you need a database, use a database, not a plain file.
– n.m.
Nov 19 at 19:58