我想在文件中找到一个字符串,并用用户输入替换它 这是我的粗略代码。
#include <iostream>
#include <fstream.h>
#include <string.h>
int main(){
istream readFile("test.txt");
string readout,
search,
replace;
while(getline(readFile,readout)){
if(readout == search){
// How do I replace `readout` with `replace`?
}
}
}
更新
这是解决我的问题的代码
的test.txt:
id_1
arfan
haider
id_2
saleem
haider
id_3
someone
otherone
C ++代码:
#include <iostream>
#include <fstream>
#include <string>
using namesapce std;
int main(){
istream readFile("test.txt");
string readout,
search,
firstname,
lastname;
cout << "Enter the id which you want to modify";
cin >> search;
while(getline(readFile,readout)){
if(readout == search){
/*
id remains the same
But the First name and Last name are replaced with
the user `firstname` and `lastname` input
*/
cout << "Enter new First name";
cin >> firstname;
cout << "Enter Last name";
cin >> lastname;
}
}
}
假设:
用户搜索ID id_2
。之后,用户输入名字和姓氏Shafiq
和Ahmed
。
运行此代码后,test.txt
文件必须修改记录:
…
id_2
Shafiq
Ahmad
…
只有id_2
记录更改,其余文件将保持不变。
答案 0 :(得分:5)
我会做@stefaanv说的话:
#include <iostream>
#include <fstream.h>
#include <string.h>
int main(){
ostream outFile("replaced.txt");
istream readFile("test.txt");
string readout;
string search;
string replace;
while(getline(readFile,readout)){
if(readout == search){
outFile << replace;
}
else {
outFile << readout;
}
}
}
编辑:如果每行的信息独立于其他行的信息,则上述解决方案有效。在您的更新中,名称行上的信息取决于id行的信息。因此,为了扩展上述技术,您需要在while循环中维护状态,以指示何时到达一个数据块的末尾。
#include <iostream>
#include <fstream.h>
#include <string.h>
int main(){
ostream outFile("replaced.txt");
istream readFile("test.txt");
string readout;
string search, Fname, Lname;
unsigned int skipLines = 0;
cout << "Enter id which you want Modify";
cin >> search;
cout << "Enter new First name";
cin >> Fname;
cout << "Enter Last name";
cin >> Lname;
while(getline(readFile,readout)) {
if (skipLines != 0) {
skipLines--;
continue;
}
else if (readout == search) {
outFile << search << endl;
outFile << Fname << endl;
outFile << Lname << endl;
skipLines = 2;
}
else {
outFile << readout;
}
}
}
稍微更优雅的方法是将每个数据块存储在结构中,这允许您使用重载的运算符&lt;&lt; &安培; &GT;取代。这使得文件读取代码和写得更清楚 - 它实际上与“每行数据独立”的情况相同。
#include <iostream>
#include <fstream.h>
#include <string.h>
struct NameRecord {
string id;
string fname;
string lname;
friend std::ostream& operator<<(std::ostream &os, const NameRecord &src);
friend std::istream& operator>>(std::istream &is, NameRecord &dst);
};
std::ostream& operator <<(std::ostream &os, const NameRecord &src) {
os << src.id << endl << src.fname << endl << src.lname << endl;
return os;
}
std::istream& operator >>(std::istream &is, NameRecord &dst) {
// may need to have more code to ignore whitespace, I'm not sure
if (is.good ()) {
is >> dst.id;
}
if (is.good ()) {
is >> dst.fname;
}
if (is.good ()) {
is >> dst.lname;
}
return is;
}
int main(){
ostream outFile("replaced.txt");
istream readFile("test.txt");
NameRecord inRecord, replaceRecord;
cout << "Enter id which you want Modify";
cin >> replaceRecord.id;
cout << "Enter new First name";
cin >> replaceRecord.Fname;
cout << "Enter Last name";
cin >> replaceRecord.Lname;
while (readFile.good()) {
// the >> operator reads the whole record (id, fname, lname)
readFile >> inRecord;
// the << operator writes the whole record
if (inRecord.id == replaceRecord.id) {
outFile << replaceRecord;
}
else {
outFile << inRecord;
}
}
}
答案 1 :(得分:5)
这应该有效。我使用string::find
在每一行中找到所需的子字符串,并使用string::replace
替换它,如果找到了某些内容。
修改:我忘记了每行多次出现这个词的情况。添加了while
来解决此问题。
#include <fstream>
#include <iostream>
using namespace std;
int main(int argc, char **argv)
{
ifstream in(argv[1]);
ofstream out(argv[2]);
string wordToReplace(argv[3]);
string wordToReplaceWith(argv[4]);
if (!in)
{
cerr << "Could not open " << argv[1] << "\n";
return 1;
}
if (!out)
{
cerr << "Could not open " << argv[2] << "\n";
return 1;
}
string line;
size_t len = wordToReplace.length();
while (getline(in, line))
{
while (true)
{
size_t pos = line.find(wordToReplace);
if (pos != string::npos)
line.replace(pos, len, wordToReplaceWith);
else
break;
}
out << line << '\n';
}
}
答案 2 :(得分:0)
#include <iostream>
#include <fstream>
using namespace std;
int main(int argc, char **argv) {
if (argc < 4) {
cout << "Invalid input" << endl;
cout << "\tchange <old_word> <new_word> <file_list>";
}
fstream fs;
string tmp;
string oldw = argv[1];
string neww = argv[2];
for (int i = 3; i < argc; i++) {
fs.open(argv[i] , ios::in);
while (!fs.eof()) {
getline(fs, tmp);
while (tmp.find(oldw) != string::npos)
tmp.replace(tmp.find(oldw), sizeof(oldw), neww);
cout << tmp << endl;
}
}
fs.close();
return 0;
}
用法:
./a.out old_word new_word filename