CODEWITHSUNDEEP
linuxqtshellqprocess
Alex
Alex

Reputation: 751

QProcess passing (shell) arguments

I'm trying to read the output of a shell script in Qt. However, passing an argument to the shell script doesn't work, as it is ignored completely. What am I doing wrong in the following excerpt?

QProcess *process = new QProcess;
process->start("sh", QStringList() << "-c" << "\"xdotool getactivewindow\"");
process->waitForFinished();
QString output = process->readAllStandardOutput();
target = output.toUInt();

I have looked at several other threads and tried solutions such as

process->start("sh", QStringList() << "-c" << "xdotool getactivewindow");

and

process->start("sh", QStringList() << "-c" << "xdotool" << "getactivewindow");

but none worked.

Upvotes: 1

Views: 2023

Answers (1)

m7913d
m7913d

Reputation: 11064

I would expect that your second method should work.

I tested it with the following script (test.sh):

#!/bin/bash
echo "First arg: $1"
echo "Second arg: $2"

And I called the script using QProcess in following ways:

QProcess *process = new QProcess;
process->start("./test.sh", QStringList() << "abc" << "xyz");
process->waitForFinished();
qDebug () << process->readAllStandardOutput();
// returns: "First arg: abc\nSecond arg: xyz\n" => OK

process->start("sh", QStringList() << "-c" << "./test.sh abc xyz");
process->waitForFinished();
qDebug () << process->readAllStandardOutput();
// returns: "First arg: abc\nSecond arg: xyz\n" => OK

process->start("sh", QStringList() << "-c" << "./test.sh" <<  "abc xyz");
process->waitForFinished();
qDebug () << process->readAllStandardOutput();
// returns: "First arg: \nSecond arg: \n" => WRONG

Explanation

  • process->start("sh", QStringList() << "-c" << "\"xdotool getactivewindow\"");: it is not needed (nor allowed) to quote the arguments yourself. The documentation is not that clear, but it states:

Note: No further splitting of the arguments is performed.

  • process->start("sh", QStringList() << "-c" << "xdotool getactivewindow");: this should work

  • process->start("sh", QStringList() << "-c" << "xdotool" << "getactivewindow");: getactivewindow is passed as an argument to sh instead of xdotool

Upvotes: 1

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