check if a application is installed

[saber]

i am in linux .
i want to know if a (mediainfo ) package is installed in system.

how can i check if package is installed by qmake and by function??

[JonB]

@saber
So far as I know, there is no "simple" test for this under Linux.

You could run an OS command (QProcess) of some kind of apt-get/apt/dpkg and parse the output (not necessarily portable across various Linux flavors), or be lazy and just check for some file existence somewhere (again, may not be portable/reliable).

[saber]

@JonB anyway to check a package from qmake??

like this cmake of pcmanfm file manger github

this lines

find_package(fm-qt REQUIRED)
find_package(lxqt-build-tools ${LXQTBT_MINIMUM_VERSION} REQUIRED)

[JonB]

@saber
Sorry, I don't use qmake, so I don't know if it can run a command/act on a return result....

[Paul Colby]

Hi @saber,

If mediainfo is a library, as defined by the pkg-config Linux command then you can use QMake's built-in packagesExist() test function (it uses pkg-config internally). However, for non-library packages, you will need to use OS-dependant tools such as dpkg for Debian-based distros, and rpm for RHEL/Fedora based distros, etc.

For example:

system(dpkg -l mediainfo > /dev/null) {
    message(mediainfo package exists)
}

You can wrap that up in your own test function pretty easily, and add Linux distro detection if necessary.

Cheers.

[JonB]

@JonB
To clarify @Paul-Colby 's code suggestion, you need to test the returns result for zero to imply package existence, e.g.:

if (system("dpkg -l mediainfo > /dev/null 2>&1") == 0) {
    message("mediainfo package exists");
}

[Paul Colby]

@JonB said in check if a application is installed:

you need to test the returns result for zero

Ah, no you don't ;)

Consider this sample:

system(dpkg -l nano > /dev/null) {
    message(nano exists)
}

!system(dpkg -l nano > /dev/null) {
    message(nano does not exist)
}

system(dpkg -l mediainfo > /dev/null) {
    message(mediainfo exists)
}

!system(dpkg -l mediainfo > /dev/null) {
    message(mediainfo does not exist)
}

Output:

Project MESSAGE: nano exists
...
Project MESSAGE: mediainfo does not exist

Whis is correct (I have nano installed, but not mediainfo).

Cheers.

[saber]

@Paul-Colby
thanks for the code.i am in arch.

what to #include for system??

and my app will run in different ditro so any other way that works on universally??

[JonB]

@Paul-Colby
Sorry, I am talking about the C system call system(), in C++ code for his "function" in runtime code. Are you perchance talking about something in cmake, which i know nothing about? I think we are talking about different things.

[JonB]

@saber

and my app will run in different ditro so any other way that works on universally??

As I said, there is nothing that will work universally across any Linux, since there is no real definition of a "package"/"application". (I am talking about your app's runtime code, I know nothing about cmake). For code for C's system() call, #include <stdlib.h>. Or you can do it via Qt's QProcess.

[Flotisable]

@JonB
I think @Paul-Colby is talking about qmake.

the qmake scope syntax and qmake build in test function system()

[JonB]

@Flotisable
Yes, I came to realise that. I was answering the OP's "and by function", which I took to mean in his app's code.