Comment by guns | Hacker News Reader

Comment by guns | Hacker News Reader

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I was intrigued by your comment and took a look at the rc feature list, but I couldn't see any features that aren't available in bash 3.1 and above.

This takes nothing away from rc of course, which was around when bash was a simple re-implementation of sh, and may very well have been the inspiration for some of bash's modern features. [1]

With regards to scripting, since perl/python/ruby has supplanted shell for moderate to difficult tasks, I think it's perfectly reasonable to use bash/zsh for the occasional simple shell script. Arch Linux, for example, writes rc scripts in modern bash, significantly increasing legibility (given you can read modern bash).

Even if you stick to sh for maximum portability, if you use bash/zsh as an interactive shell, I would strongly encourage diving into the man page; modern shells, for all their shell\ quoting woes, have an amazing amount of concise constructs that make life at the command line quite pleasurable.

[1]: More likely is that Korn shell is the inspiration for both

The main feature that Rc has which Bash lacks is simplicity. Bash's man page is twice the size of Rc's entire source code.

I'm not an rc expert, merely a disgruntled POSIX shell scripter, so here are some attractive rc features [1] missing from sh and bash:

> Rc captures command exit status in the variable $status. For a simple command the value of $status is just as described above. For a pipeline $status is set to the concatenation of the statuses of the pipeline components with | characters for separators.

Both bash and ksh have the pipefail option, which at least makes the pipeline fail if any component fails. (Horrifyingly, POSIX sh lacks even this.) Actually seeing which component failed can be really handy. In other shells, you only get $?.

> Arbitrary file descriptors may be sent through a pipe by typing, for example, "vc junk.c |[2] grep -v ’^$’" This deletes blank lines from the C compiler’s error output.

POSIX sh, bash, and ksh can only connect stdout to stdin across a pipe. Connecting arbitrary descriptors is nice, particularly in logging applications.

> There is no need for the distinction between $* and $@. There is no need for four types of quotation, nor the extremely complicated rules that govern them.

How many people understand the difference between $* and $@ in POSIX sh or bash, or for instance the difference between "$@" and $@? These are critical things any POSIX shell scripter should know, yet I've met very few that actually do. One approach is to educate people about these things. Another is to avoid the need to educate them in the first place.

I like that rc cleans up quoting, which I've seen single-handedly scare developers off of shell scripting.

[1] http://doc.cat-v.org/plan_9/4th_edition/papers/rc

so you call one command and want just to know if it failed... but that command triggered a series of pipes internally, now you have to trim the status mess?

thankfully truly posix stuff doesn't have it

but that command triggered a series of pipes internally, now you have to trim the status mess?

No. If you run an external command from an rc script, ie the shell is doing the fork and exec for you, then $status will have a single number just like $?.

It doesn't matter if the external command is an rc script that, internally, runs a pipeline at the end. You will only get a multi-status if the previous statement within the current rc script was a pipeline. Under sh, bash, or ksh, people rarely bother to look at $? in this situation, since it's either potentially irrelevant (without -o pipefail), or you don't know which program it's from (with -o pipefail).

so you call one command and want just to know if it failed

This works perfectly fine in rc:

   find . | grep '[0-9]' | wc || echo >[1=2] "number files not found"

From the rc docs:

> Any $status containing only 0’s and |’s has boolean value true. Any other status is false.

rc solves problems with sh by replacing annoying/problematic features. bash adds the same features, but keeps all the problems with sh. Read the "Design Principles" section for specific examples.

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