TLDR: you are currently relying on unspecified behaviour of signal(2); use sigaction (carefully) instead. Firstly, SIGCHLD is strange. From the manual page for sigaction; POSIX.1-1990 disallowed setting the action for SIGCHLD to SIG_IGN. POSIX.1-2001 allows this possibility, so that ignoring SIGCHLD can be used to prevent the creation of zombies (see wait(2)). Nevertheless, the historical … Read more
I do understand I’m adding an answer to an old question, but I feel the tooling has improved lately and would like to give additional suggestions in order to help out others who are viewing this question. I have recently found TomDoc.sh, which uses TomDoc style comments in shell scripts. The tool provided can then … Read more
In Arch, /bin/sh is a symlink to /bin/bash, which has quite a few rules about startup scripts, with special cases when called sh : If bash is invoked with the name sh, it tries to mimic the startup behavior of historical versions of sh as closely as possible, … If you start it from the … Read more
The key difference between these is that older versions of the busybox image statically linked busybox against glibc (current versions dynamically link busybox against glibc due to use of libnss even in static configuration), whereas the alpine image dynamically links against musl libc. Going into the weighting factors used to choose between these in detail … Read more
Globbing is the * and ? and some other pattern matchers you may be familiar with. Globbing interprets the standard wild card characters * and ?, character lists in square brackets, and certain other special characters (such as ^ for negating the sense of a match). When the shell sees a glob, it will perform … Read more
kernel.org has a public (read-only) git repository that you can clone. It has also tags for every kernel version, so you can checkout a specific version: # Clone the kernel to your local machine $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git $ cd linux-stable # Find the tag for the version you want $ git tag -l | … Read more
First, let’s demonstrate that head is actually working correctly: $ printf ‘\xef\xbb\xbf’ >file $ head -c 3 file $ head -c 3 file | hexdump -C 00000000 ef bb bf |…| 00000003 Now, let’s create a working function has_bom. If your grep supports -P, then one option is: $ has_bom() { head -c3 “$1” | … Read more
It’s something introduced in C99 which lets the compiler know that the pointer passed in there isn’t pointing to the same place as any other pointers in the arguments. If you give this hint to the compiler, it can do some more aggressive optimizations without breaking code. As an example, consider this function: int add(int … Read more
You can install aspell with Homebrew on OS X. brew info aspell lists supported languages. brew install aspell –lang=en,fi,jp aspell check opens a file in an interactive spell checker: for f in *.txt; do aspell check $f; done aspell list prints all unrecognized words: cat *.txt | aspell list | sort -u Learned words are … Read more
Find the module in the sysfs tree. In this case it was in /sys/bus/usb-serial/drivers/cp2101 In this directory, there is a new_id file entry that can be used to dynamically add VID PID pair like this : echo VID PID >new_id Here is a LWN entry about this feature