https://frn.sh/til_/Recent content in til on Fernando SimõesHugoen-USCopyright © Fernando Simões.Sun, 18 May 2025 00:00:00 +0000https://frn.sh/til_/osync/Sun, 18 May 2025 00:00:00 +0000https://frn.sh/til_/osync/write(2) doesn’t actually write to disk imediatelly. Instead, it writes to a page cache and the OS periodically handles writes to disk. Using O_SYNC, though, write(2) returns only when it fully wrote the data to a data block. Linux exposes the actual timeframe for periodic writings: ➜ ~ cat /proc/sys/vm/dirty_writeback_centisecs 500https://frn.sh/til_/source-and-export/Sun, 05 Jan 2025 00:00:00 +0000https://frn.sh/til_/source-and-export/Non-interactive shells don’t load initialization files, so bash -c ‘declare -f’ doesn’t output anything. But we can source it: bash -c ‘source ~/.bashrc; hello’. Or even: bash -c ‘hello() { echo “hi”; }; declare -f’. It’s all about memory share in shell modes: source changes only affect current shell memory. export marks variables to be passed to child processes. Subtile difference that can save us a lof of debugging time.