Two Linux-specific methods are SA_SIGINFO and signalfd(), which allows programs to receive very detailed information about signals sent, including the sender’s PID. Call sigaction() and pass to it a struct sigaction which has the desired signal handler in sa_sigaction and the SA_SIGINFO flag in sa_flags set. With this flag, your signal handler will receive three … Read more
You can choose: if [[ $? -ne 0 ]]; then # -ne: not equal if ! [[ $? -eq 0 ]]; then # -eq: equal if [[ ! $? -eq 0 ]]; then ! inverts the return of the following expression, respectively.
tl;dr: When PowerShell pipes a string to an external program: It encodes it using the character encoding stored in the $OutputEncoding preference variable It invariably appends a trailing (platform-appropriate) newline. Therefore, the key is to avoid PowerShell’s pipeline in favor of the native shell’s, so as to prevent implicit addition of a trailing newline: If … Read more
This is because grep -q exits immediately with a zero status as soon as a match is found. The zfs command is still writing to the pipe, but there is no reader (because grep has exited), so it is sent a SIGPIPE signal from the kernel and it exits with a status of 141. Another … Read more
You can use the fuser command, which is part of the psmisc package, like: fuser file_name You will receive a list of processes using the file. You can use different flags with it, in order to receive a more detailed output. You can find more info in the fuser’s Wikipedia article, or in the man … Read more
GCC only does this extra stack alignment in main; that function is special. You won’t see it if you look at code-gen for any other function, unless you have a local with alignas(32) or something. GCC is just taking a defensive approach with -m32, by not assuming that main is called with a properly 16B-aligned … Read more
It looks like there is a nice workaround for this implemented in recent versions of glibc: a “tunables” feature that guides selection of optimized string functions. You can find a general overview of this feature here and the relevant code inside glibc in ifunc-impl-list.c. Here’s how I figured it out. First, I took the address … Read more
Turns out there isn’t a way to reliably recover the semaphore. Sure, anyone can post_sem() to the named semaphore to get the count to increase past zero again, but how to tell when such a recovery is needed? The API provided is too limited and doesn’t indicate in any way when this has happened. Beware … Read more
You can use the Linux Bash core utility split: split -b 1M -d file.txt file Note that M or MB both are OK but size is different. MB is 1000 * 1000, M is 1024^2 If you want to separate by lines you can use -l parameter. UPDATE a=(`wc -l yourfile`) ; lines=`echo $(($a/12)) | … Read more
From man 2 write, you can see the signature of write is, ssize_t write(int fd, const void *buf, size_t count); It takes a pointer (const void *buf) to a buffer in memory. You can’t pass it a char by value, so you have to store it to memory and pass a pointer. (Don’t print one … Read more