How to check is there is a string that I want?

victor wang

Hi All,
I'm using qt5.5 on my computer.
I wanna know is there a string that I want in a QString.
After reading some document, I'm using indexof() to do it.

I'm using this to get my QString.

QString wifi_ping = "ping -I eth0 www.google.com.tw -c 1";
Process::executeProcessSync(QString("sh"),QStringList()<<"-c"<<wifi_ping,&wifi_message);

This is what I got in my QString.

PING 192.168.120.112 (192.168.120.112) from 192.168.120.115 eth0: 56(84) bytes of data.
64 bytes from 192.168.120.112: icmp_seq=1 ttl=64 time=0.321 ms

--- 192.168.120.112 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.321/0.321/0.321/0.000 ms

And I check it in my program like below.

if(wifi_message.indexof("bad"))
{
     qDebug("Failed");
}
else if(wifi_message.indexof("ping statistics"))
{
     qDebug("pass");
}

Unfortunately, It will always goes Failed.
And i check the document, I am sure there is no "bad" string.
Why it will show Failed every time?

Thanks in Advance!

joeQ

@victor-wang hi,friend,welcome.

int QString::indexOf(const QString &str, int from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
Returns the index position of the first occurrence of the string str in this string, searching forward from index position from. Returns -1 if str is not found.
If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.
If from is -1, the search starts at the last character; if it is -2, at the next to last character and so on.

qDebug() << wifi_message; ///< to see the string content
///< you can to putout the result
//qDebug() << wifi_message.indexof("bad");
if(0 <= wifi_message.indexof("bad")){
     qDebug("Failed");
}else if(0 <= wifi_message.indexof("ping statistics")){
     qDebug("pass");
}

try again.

raven-worx

@victor-wang said in How to check is there is a string that I want?:

if(wifi_message.indexof("bad"))
{
qDebug("Failed");
}
else if(wifi_message.indexof("ping statistics"))
{
qDebug("pass");
}

your checks are not correct (false-positive)!
In case it doesn't find the string "bad" -1 is returned. In C++ everything that is not equal zero is true when implicitly converted to bool.

So your checks should rather look like this:

if(wifi_message.indexof("bad") >= 0)
{
     qDebug("Failed");
}
else if(wifi_message.indexof("ping statistics") >= 0)
{
     qDebug("pass");
}

victor wang

@joeQ
Thanks it works now!

victor wang

@raven-worx
Thanks it works now!