part II: Remove multiple whitespace-lines from a file

Written by marcelpetrick on May 7, 2015

I was so annoyed that the simple idea with sed did not worked like I wanted, that I wrote a short full-fledged Qt-appp for it. Code follows. Just compile the main.cpp. Usage is also explained in the header of the file.
I know it’s like to break a butterfly on a wheel, but I need this functionality since I don’t want to do such a boring task like code-styling by myself ..

Update: first version had a small glitch! Found after applying it to some bigger files.

//! @brief  lessWhite should remove all multiple empty lines (newline, whitespace, tabs, spaces, ...) from the given input.
//!         Based on the standard POSIX channels stdin, stdout, stderr.
//!         usage like: $ ./lessWhite < input.txt > output.txt
//!         terminal output will look like: "removed 67 lines!"
//! @author mail@marcelpetrick.it
//! @version    0.02 (bugfix for "output had one additional newline at the end")
//!
//! history: 0.01: initial state

#include <QTextStream>
#include <QString>

int main(int argc, char *argv[])
{
    Q_UNUSED(argc);
    Q_UNUSED(argv);

    QTextStream stream(stdin);
    QString output; //the combined stuff: no checks for overflow
    QString line;
    bool lastWasEmpty(false);
    int removedLines(0);
    bool isVeryFirstLine(true);

    do
    {
        line = stream.readLine();
        bool const currentIsEmpty(line.trimmed().isEmpty());

        if(currentIsEmpty && lastWasEmpty)
        {
            removedLines++; //do nothing
        }
        else
        {
            if(!isVeryFirstLine) //prevent the bug with the last line == double newline
            {
                output.append("\n");
            }
            else
            {
                isVeryFirstLine = false; //reset now
            }

            output.append(line);
        }

        lastWasEmpty = currentIsEmpty;

    } while(!line.isNull());

    //output
    QTextStream cout(stdout);
    cout << output; //print to stdout

    QTextStream cerr(stderr);
    cerr << "removed " << removedLines << " lines!\n"; //print to stderr
}

//! @brief lessWhite should remove all multiple empty lines (newline, whitespace, tabs, spaces, ...) from the given input.

//! Based on the standard POSIX channels stdin, stdout, stderr.

//! usage like: $ ./lessWhite < input.txt > output.txt

//! terminal output will look like: "removed 67 lines!"

//! @author mail@marcelpetrick.it

//! @version 0.02 (bugfix for "output had one additional newline at the end")

//!

//! history: 0.01: initial state

#include <QTextStream>

#include <QString>

int main(int argc, char *argv[])

{

Q_UNUSED(argc);

Q_UNUSED(argv);

QTextStream stream(stdin);

QString output; //the combined stuff: no checks for overflow

QString line;

bool lastWasEmpty(false);

int removedLines(0);

bool isVeryFirstLine(true);

{

line = stream.readLine();

bool const currentIsEmpty(line.trimmed().isEmpty());

if(currentIsEmpty && lastWasEmpty)

{

removedLines++; //do nothing

}

else

{

if(!isVeryFirstLine) //prevent the bug with the last line == double newline

{

output.append("\n");

}

else

{

isVeryFirstLine = false; //reset now

}

output.append(line);

}

lastWasEmpty = currentIsEmpty;

} while(!line.isNull());

//output

QTextStream cout(stdout);

cout << output; //print to stdout

QTextStream cerr(stderr);

cerr << "removed " << removedLines << " lines!\n"; //print to stderr

}

solutions; not code

part II: Remove multiple whitespace-lines from a file

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