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coltson
n00b
Joined: 15 Oct 2005
Posts: 54
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 Posted: Mon Feb 18, 2013 11:10 pm Post subject: Don't know character necessary to read file line to string |
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I am reading a file and want to compare the content from the first line of this file to a certain word. Here is what I am trying to do:
| Code: | getline (fileReader,line);
if (line == "Image")
cout << "Wellingtton Paulista" << endl; |
Here is the beginning of the file
| Quote: | Image
///////////////////////////////////////// |
As can be seen, my idea is that line is equal to "Image", so the expression is evaluated to true and then cout is executed.
But is not working. I suspected there is a end line character that it is being read and stored together with Image.
However when I put a | Code: | | cout << line << endl; |
it just prints . But if I put a before the if expression it works as intended. So what character I should put in the getline so it just captures the "Image"? I tried | Code: | | getline (fileReader,line,'\n') |
and it didn't work.
Thanks for any help |
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lexflex
Guru
Joined: 05 Mar 2006
Posts: 363
Location: the Netherlands
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| Posted: Tue Feb 19, 2013 6:00 am Post subject: |
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Hi,
I think you can use wildcards ( someting like *mage* ).
Alex.
PS: Sorry, not bash ( I was just doing something similar in a shellscript...). |
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John R. Graham
Administrator
Joined: 08 Mar 2005
Posts: 10587
Location: Somewhere over Atlanta, Georgia
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| Posted: Tue Feb 19, 2013 3:26 pm Post subject: |
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What's the declaration of the variable "line"? The normal C++ getline function should discard the newline character. For example, the following trivial example behaves as expected: | Code: | #include <iostream>
#include <string>
using namespace std;
int main(void) {
string line;
do {
getline(cin, line);
if (line == "John")
cout << "Hello, " << line << ".\n";
} while (! cin.eof());
return 0;
} |
- John
_________________
I can confirm that I have received between 0 and 499 National Security Letters. |
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aderesch
Tux's lil' helper
Joined: 06 Mar 2010
Posts: 123
Location: Hamburg, Germany
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| Posted: Tue Feb 19, 2013 5:56 pm Post subject: |
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| John R. Graham wrote: | | The normal C++ getline function should discard the newline character. |
Won't discard \r, though. The file probably has CRLF line endings.
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Hu
Moderator
Joined: 06 Mar 2007
Posts: 21595
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| Posted: Wed Feb 20, 2013 2:31 am Post subject: |
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| aderesch wrote: | | John R. Graham wrote: | | The normal C++ getline function should discard the newline character. |
Won't discard \r, though. The file probably has CRLF line endings. |
That might be a problem if the input came from Windows, but most Linux editors save files with the proper line endings. |
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coltson
n00b
Joined: 15 Oct 2005
Posts: 54
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| Posted: Wed Feb 20, 2013 3:29 am Post subject: |
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| John R. Graham wrote: | | What's the declaration of the variable "line"? |
| Code: | private:
std::string line; |
I don't know from where the file came from, but I tested with | Code: | | getline(cin, line,'\r'); |
and now it is working as a charm. However, if I create a file from zero, and insert "Image" as the first line it doesn't work.
That makes me to imagine that getline is only looking for '\r' and not for '\r' and '\n' as I would like
So there is a way it can work with both kind of files simultaneously? |
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aderesch
Tux's lil' helper
Joined: 06 Mar 2010
Posts: 123
Location: Hamburg, Germany
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| Posted: Wed Feb 20, 2013 6:43 am Post subject: |
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| Hu wrote: | | That might be a problem if the input came from Windows, but most Linux editors save files with the proper line endings. |
We didn't know anything about the origin of the file. In my experience this is _by far_ the most probable explanation for this kind of problem.
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aderesch
Tux's lil' helper
Joined: 06 Mar 2010
Posts: 123
Location: Hamburg, Germany
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| Posted: Wed Feb 20, 2013 6:52 am Post subject: |
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| coltson wrote: | I don't know from where the file came from, but I tested with | Code: | | getline(cin, line,'\r'); |
and now it is working as a charm. However, if I create a file from zero, and insert "Image" as the first line it doesn't work.
That makes me to imagine that getline is only looking for '\r' and not for '\r' and '\n' as I would like
So there is a way it can work with both kind of files simultaneously? |
Of course there is. The question is how generic a solution you want/need.
If \n and \r\n are the only variants to check for (should be sufficient for all Win/Unix text files): use getline, test for \r as the last character and remove if found.
Beware: There are files which have only \r as a line ending, and even \n\r have been seen before. Read the Wikipedia article on "Newline" for details.
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John R. Graham
Administrator
Joined: 08 Mar 2005
Posts: 10587
Location: Somewhere over Atlanta, Georgia
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| Posted: Wed Feb 20, 2013 1:45 pm Post subject: |
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Why try to make *nix programs accommodate DOS file formats? Just convert the file to proper *nix format before processing it with your program. See app-text/dos2unix.
- John
_________________
I can confirm that I have received between 0 and 499 National Security Letters. |
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dmitchell
Veteran
Joined: 17 May 2003
Posts: 1159
Location: Austin, Texas
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| Posted: Sun Feb 24, 2013 6:04 am Post subject: |
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Depending on your application it might be acceptable to check if the line begins with "Image" instead of being equal to "Image".
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Your argument is invalid. |
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