Tom Christiansen's Csh Programming Considered Harmful used to be postedto various Usenet comp.unix groups, nigh on ten years ago or so. Iconsider it sort of a pity that it isn't still being posted, becauseevery so often someone still decides that writing shell scripts in csh would be a good idea.

Some of the problems Christiansen identified have since been fixed bymodern versions of tcsh , but not all of them.

(The article can also serve as an interesting catalog of sh programming tricks.

Something I've discovered through (painful) experience is that threadedprograms cannot portably fork() in one thread and then wait() forthe forked process in another one.

This will work in some environments but fail explosively in others; theone I stubbed my toe on was a Linux 2.4 kernel based system (without NPTL , which is the usual state of affairsfor 2.4-based Linux distributions).

Admittedly, mixing threads and fork() is a bit perverse, butsometimes it

Presented in the traditional illustrated form:

; dig +short ns hinet.net.tw.reg.hinet.net.tw.www.hinet.net.tw.hinet.net.tw.

This looks good, except for the fact that they all have the sameIP address, 210.65.1.231. You would think that a large TaiwaneseISP would be able to afford more than one DNS server, but perhapsthey're too busy beefing up their network

This one is a close variation of HowNotToDoDNSIX , but it earns extrapoints for making the reverse error from a common one. Presented insemi-illustrated format:

; dig +short ns system-bank.net.dns01.system-bank.net.dns02.system-bank.net.

(At this point I will pause to note that dns01.system-bank.net anddns02.system-bank.net have the same IP address, 218