Intel CPUs after Core Duo support two Model-Specific registers called IA32_MPERF and IA32_APERF. MPERF counts at the maximum frequency the CPU supports, while APERF counts at the actual current frequency. The actual frequency is given by: You can read them with this flow ; read MPERF mov ecx, 0xe7 rdmsr mov mperf_var_lo, eax mov mperf_var_hi, … Read more
System calls are operating system functions, like on UNIX, the malloc() function is built on top of the sbrk() system call (for resizing process memory space). Libraries are just application code that’s not part of the operating system and will often be available on more than one OS. They’re basically the same as function calls … Read more
Say you have a file with many empty bytes \x00. These many empty bytes \x00 are called holes. Storing empty bytes is just not efficient, we know there are many of them in the file, so why store them on the storage device? We could instead store metadata describing those zeros. When a process reads … Read more
Both Debian and Ubuntu ship with pam_umask. This allows you to configure umask in /etc/login.defs and have them apply system-wide, regardless of how a user logs in. To enable it, you may need to add a line to /etc/pam.d/common-session reading session optional pam_umask.so or it may already be enabled. Then edit /etc/login.defs and change the … Read more
Correct. If the exec works, the perror will not be called, simply because the call to perror no longer exists. I find it’s sometimes easier when educating newcomers to these concepts, to think of the UNIX execution model as being comprised of processes, programs and program instances. Programs are executable files such as /bin/ls or … Read more
system(“PAUSE”) is certainly less than ideal. using a call to system creates a subprocess, which on windows is fairly expensive and in any case not terribly cheap on any operating system. On embedded systems the memory overhead is significant. If there is any way to do it without much pain natively then do it. In … Read more
Give a try with (that is, surrounding cuobjdump.exe path with “, properly escaped in C++ as \”): system(“\”C:\\program files\\nvidia gpu computing…\\cuobjdump.exe\” –dump-cubin C:\\..\\input.exe”);
That depends on the shell being invoked to execute the commands, but in general most shells use ; to separate commands so something like this should work: command1; command2; command3 [EDIT] As @dicroce mentioned, you can use && instead of ; which will stop execution at the first command that returns a non-zero value. This … Read more
The problem is that some program has been set to autorun when you run cmd.exe. In my case it was ANSICON that was installed… and then I moved the file without properly uninstalling. I found a solution in this blog post: http://carol-nichols.com/2011/03/17/the-system-cannot-find-the-path-specified/ The short version is to find HKCU\Software\Microsoft\Command Processor\AutoRun and clear the value.
system(): runs command and returns command’s exit status backticks: runs command and returns the command’s output pipes : runs command and allows you to use them as an handle Also backticks redirects the executed program’s STDOUT to a variable, and system sends it to your main program’s STDOUT.