On Tue, Nov 12, 2024 at 11:24:59 +0100, to...@tuxteam.de wrote: > On Tue, Nov 12, 2024 at 10:08:18AM +0000, Corey wrote: > > Hello > > > > Do you know in C language what's the better way to get the info like the > > output by lsb_release? > > > > $ lsb_release -cd > > Description: Ubuntu 22.04.3 LTS > > Codename: jammy > > > > > > i know there is system call. but is there a native way? > > I don't think there is a special system call for that. Have you had a > look at the command itself? It is a shell script, and looks pretty > pedestrian to me (at first sight, granted).
I think Corey might be confused about the term "system call". Most people use "system call" to mean an invocation of a subroutine within the kernel. These system calls are documented in section 2 of the man pages, so e.g. "read(2)" is a system call that reads bytes from an open file descriptor. For the official explanation of a system call, see <https://manpages.debian.org/bookworm/manpages/intro.2.en.html> or "man 2 intro" if you have this section installed locally. I *suspect* that Corey thought "system call" meant the use of the system(3) library function, which executes a shell command. As tomas points out, lsb_release is a relatively short shell script, and you can read it to see what it's doing. Ultimately, it's reading data from /etc/os-release (or /usr/lib/os-release), parsing it, and printing pieces of it. You could write a C program to do the same steps.
