Links: 4th Sep

September 4, 2013

§ links # apple • grep • iphone • kids • less • osx • photos • recording • rpmdb • SA • scale • signals • sunlight • yac

This week: technology links and a chart with sunlight hours.

grep tricks: grep files recursively, show only filenames where matching string was/wasn’t found.
Did you know that:
- $ less <directory> — shows directory listing
- $ less <archive.zip> — shows archive content
Teacher’s rumblings “Kids can’t use computers“. Agree to a T.
Going back to iPhone [from Android]. Again having pretty much the same thoughts.
Reddit: Lessons Learned From Mistakes Made Scaling To 1 Billion Pageviews A Month
Start a Web Search in a GUI Browser from the Command Line on Mac OS X
Screen recording to an animated GIF on Mac OS X
How to know from a child process that its parent exited:
- a pipe between parent and a child, child gets SIGPIPE when parent exits
- if a child has not detached, PPID becomes 1 when parent exits
- Linux-specific: a child can ask kernel to deliver a signal when parent dies by specifying option PR_SET_PDEATHSIG in prctl() syscall
Two talks from YAC which I liked:
- Small service administration
- Fault-tolerance and load balancing
rpmdb locking issues, notorious on RHEL4/5, manifest as a hanging rpm command. To see active locks:
```
# cd /var/lib/rpm; /usr/lib/rpm/rpmdb_stat -CA
```
Normally there should be no locks, given no rpm command is running. In case there are stale locks, just remove __db.00* files.