I'm creating a program in which I get the path of a file, then send it as a parameter into another program. The problem is when I get the path, it has the special character '\', which completely mess up the string I send to the other program. Is there a way I can ignore the escape character or change it to '/'?
Thanks!!
To change the \ to /, a simple iteration over the string should suffice. The required code is:
's' is assumed to be the concerned string.
for (int i = 0; i < s.length(); i++)
{
if (s[i] == `\`)
s[i] = `/`;
}
Please elaborate your question. The problem may be with second program.
First Program may be :
char str1[50]="start abc.exe ";
char str2[20];
cin>>str2;
strcat(str1,str2);
system(str1);
Second program may be (abc.exe) :
int main(int argc,char *argv[])
{
for(i=1;i<argc;i++)
{
cout<<argv[i]<<" \n";
}
}
This is just an example.
Related
This may be a little bit redundant, but is there a short/compact method of reading in a string until a tab is reached in C++? Similar to other questions, but I want to keep reading even if I hit a space. For example if the STDIN is
Cute Kitty is fabulous as always
Then I want to read in Cute Kitty; is; fabulous as always, three times.
I've seen people do this with regex in files, but how would you do this on the stdin in C++? I want to put it in a string class and whenever I try something like
scanf("%s\t", &mystring);
It throws up an error because I'm not using an array of chars.
Thanks, please keep answers easy enough for a noob to understand.
This code seems to work for me. It basically gets the line that was entered from the user via stdin and then reads each character waiting for a tab character (\t), or the end of the line.
#include <iostream>
#include <string>
int main()
{
std::string a;
std::getline(std::cin,a);
int index_holder = 0;
for(std::string::size_type i = 0; i < a.size(); ++i)
{
if(a[i] == '\t' || (i == a.size() - 1)) {
std::cout << a.substr(index_holder, i - index_holder) << std::endl;
index_holder = i + 1;
}
}
return 0;
}
Have a look at strtok:
char * strtok ( char * str, const char * delimiters );
Split string into tokens. A sequence of calls to this function split str into tokens, which are sequences of contiguous characters separated by any of the characters that are part of delimiters.
I want to reverse the letters of the words in a string and have to store it in the same array.example: i/p: hi how are you o/p: ih woh era uoy. i wrote this programs but it just prints the same string without reversing and the program is not terminating it continues to print something. i cant findout the mistake. please help me and tell me the correct code.
#include<iostream.h>
#include<conio.h>
#include<stdio.h>
void stre(char (&a1)[20], int j1, int i1)
{
char b[20];
for(int k=i1-j1;k<i1;k++)
b[k]=a1[i1-k-1];
for(k=i1-j1;k<i1;k++);
a1[k]=b[k];
}
void main()
{
clrscr();
int j;
char a[20];
gets(a);
for(int i=0;a[i]!='\0';i++)
{
j++;
if(a[i]==' ')
{
stre(a,j,i);
j=0;
}
}
stre(a,j,i);
for(j=0;j<i;j++)
cout<<a[j];
getch();
}
friends after your answers i removed the semicolon in the for loop and also initialized j=0 but still i am not able to get the required output now for the i/p:hi how are you o/p:ihh hi hhi hhi. still need your help.
for(k=i1-j1;k<i1;k++);
a1[k]=b[k];
The semilcolon after the for loop prevents the last action from occuring multiple times.
try
#include <iostream>
using namespace std;
int main() {
int j =0;
char a[20] = "hi how are you";
char b[20] = "";
int l=0;
for(int i=0;a[i]!='\0';i++){
if(a[i]==' ' ||a[i+1]=='\0'){
cout<<j<<' '<<i;
if(a[i+1]=='\0'){
b[l++] = ' ';
}
for(int k=i;k>=j;k--){
b[l]=a[k];
l++;
}
for(int k=j;k<=i;k++){
cout<<b[k];
a[k] = b[k];
}
cout<<endl;
j = i+1;
}
}
cout << a;
return 0;
}
This for loop is terminated by the semi-colon:
for(k=i1-j1;k<i1;k++);
^^^
Here's a version that is not perfect by any means, but at least, it tries to be more like C++ than C:
http://ideone.com/f5vciW
first: tokenize into words and space sequences
//the spaces should be preserved
std::string test("hi how are you"),reference("ih woh era uoy");
std::vector<std::string> tokens;
tokenize(test,tokens);
then reverse the tokens
for (auto& token : tokens)
std::reverse(token.begin(),token.end());
assemble tokens into a string buffer
std::stringstream buf;
for (auto token : tokens)
buf<<token;
check the result
std::string res=buf.str();
assert(res==reference);
where the tokenizer looks like that:
template <typename TContainer,typename TString>
void tokenize(TString input,TContainer& res)
{
if (input.length()<2) {
res.push_back(input);
return;
}
typename TString::const_iterator pos=input.begin();
bool space_state=std::isspace(input[0],std::locale());
for (typename TString::const_iterator it=input.begin(); it!=input.end();
++it) {
bool is_space=std::isspace(*it,std::locale());
if (is_space!=space_state) {
res.push_back(TString(pos,it));
pos=it;
space_state=is_space;
}
}
//the rest
if (pos!=input.end()) {
res.push_back(
TString(
pos,
static_cast<typename TString::const_iterator>(input.end())
));
}
}
you passed j without assigning the value. so it will be garbage.
I can see two things in your code that may not result in the expected output:
1)
int j;
should be replaced with
int j=0;
And
for(k=i1-j1;k<i1;k++);
a1[k]=b[k];
the semicolon after the for loop needs to be removed.
FYI, this mixing of C and C++ code is not recommended (it's compromising readability). please stick to either one of them.
A similar example is shown on this site. They've also used almost the same approach that you'v e chosen(reversing each word by counting number of spaces) by with the help of stack data structure.
Make sure you have the STL library installed in your environment to run this code. Better run this code on linux platform.
Here's another, shorter version, doing the inversion in-line without using an extra buffer:
http://ideone.com/hs9NZ7
the criterion for the tokenizer is the change in the isspace condition:
auto next_token=
[&](char c) {
return std::isspace(c,loc)!=std::isspace(*pos,loc);
};
using that we can go through the input string and visit the tokens:
for (auto it=std::find_if(pos,test.end(),next_token);
it!=test.end();
it=std::find_if(pos,test.end(),next_token))
reversing them and updating the current position
std::reverse(pos,it);
pos=it;
and not forgetting the leftover token.
I'm a little confused by the class code. Here's what I'm trying to do:
//Program takes "string text" and compares it to "string remove". Any letters in
//common between the two get deleted and the remaining string gets returned.
#include <string>
#include "genlib.h"
string CensorString1(string text, string remove);
int main() {
CensorString1("abcdef", "abc");
return 0;
}
string CensorString1(string text, string remove) {
for (int i = 0; text[i]; i++){
for (int n = 0; remove[n]; n++){
if (i != n){
string outputString = ' '; //to store non repeated chars in,
//forming my return string
outputString += i;
}
}
}
return outputString;
}
I'm getting an error on the "outputString += 1" saying: "cannot convert from "char" to
std::basic_string
I'm also getting an error on the "return outputString" saying: undeclared identifier
???????
I get that I'm putting a "char" on a "string" variable but what if shortly that "char" will soon be a string? Is there a way to pass this?
I'm always forgetting libraries. Can someone recommend a couple of standard/basic libraries I should always think about? Right now I'm thinking , "genlib.h" (from class).
C++ is kicking my ass. I can't get around constant little errors. Tell me it's going to get better.
There are many errors in your code:
Your outputString needs to be in the outer scope (syntax)
You compare i to n instead of text[i] to remove[n] (semantic)
You are adding i to the output instead of text[i] (semantic)
You ignore the return of CensorString1 (semantic)
Here is your modified code:
string CensorString1(string text, string remove) {
string outputString;
for (int i = 0; text[i] ; i++){
for (int n = 0; remove[n] ; n++){
if (text[i] != remove[n]){
outputString += text[i];
}
}
}
return outputString;
}
This has some remaining issues. For example, using text[i] and remove[n] for termination conditions. It is also very inefficient, but it should be a decent start.
At any rate, strings are always double-quoted in C and C++. Single-quoted constants are char constants. Fix that and you should probably be all right.
Also, look at this SO question: How do you append an int to a string in C++?
Good luck at Stanford!
There are some problems there:
string outputString = ' '; will try to construct a string from a char, which you can't do. You can assign a char to a string though, so this should be valid:
string outputString;
outputString = ' ';
Then, outputString is only visible within your if, so it won't act as an accumulator but rather be created and destroyed.
You're also trying to add character indices to the string, instead of characters, which is not what I think you want to be doing. It seems like you're mixing up C and C++.
For example, if you want to print the characters of a string, you could do something like:
string s("Test");
for (int i=0;i<s.length();i++)
cout << s[i];
Finally, I'd say that if you want to remove characters in text that also appear in remove, you'd need to make sure that none of the characters in remove match your current character, before you add it to the output string.
This is an implementation of what I think you want, your code has multiple problems which just showed up described in multiple other answers.
std::string CensorString1(std::string text, std::string remove) {
std::string result;
for (int i = 0; i<text.length(); i++) {
const char ch = text[i];
if(remove.find(ch) == -1)
result.append(1,ch);
}
return result;
}
I have a required where i need to extract a number from a string in the needed format like :
f001-->100
f100-->1
2030-->302
0203-->3020
2031-->1302
so the operation above is :
remove any f character if it is present
reverse the string
remove leading zeros from the string
I have written a code which is working fine in c++:
int main(int argc,char* argv[])
{
string str1(argv[argc-1]);
reverse(str1.begin(),str1.end());
str1.erase(remove(str1.begin(),str1.end(),'f'),str1.end());
str1.erase(0,str1.find_first_not_of('0',0));
cout <<str1<<endl;
return 0;
}
is there any better way of doing the same thing?
I Guess, a simple function as below will do the job
NOTE:- It is not a complete program. Just a flow... It will parse the string once in stead of 3 times as in your case. I definitely hope there are better C++ style approach, and looking forward to the same.
foo(char* str) {
int state=0;
int len=strlen(str);
for(i=len-1; i>=0; i++) {
if(state==0 && str[i]!='0') { //Ignore trailing zeros
state=1;
}
else if(stare==1) {
if(str[i]=='f')
break;
//Reverse logic here, just store the char in a heap as it comes which will be returned after the for finishes
}
}
}
I am currently trying to read a file, put extra backward slash () if it finds a backward slash, and write it to another file. The problem is, there are weird characters being printed inside the path.txt. I suspect that, the space characters from the file logdata is the root of this problem. Need advice how to solve this.
Here is the code:
// read a file
char str[256];
fstream file_op("C:\\logdata",ios::in);
file_op >> str;
file_op.close();
// finds the slash, and add additional slash
char newPath[MAX_PATH];
int newCount = 0;
for(int i=0; i < strlen(str); i++)
{
if(str[i] == '\\')
{
newPath[newCount++] = str[i];
}
newPath[newCount++] = str[i];
}
// write it to a different file
ofstream out("c:\\path.txt", ios::out | ios::binary);
out.write(newPath, strlen(newPath));
out.close();
Every char string in C has to end with character \0. It is an indicator that the string ends right there.
Your newPath array, after iterating through your for-loop is not correctly ended. It probably ends somewhere later, where \0 appears by accident in memory.
Try doing the following right after exiting the for-loop:
newPath[newCount]=0;
A safer way for using strings in C++, is to use std::string class over plain char arrays.
Try putting a string terminator in the buffer, after the loop :
newPath[newCount] = 0;