Shell Programming and Scripting

@cfajohnson

Off topic, but this current tread shows what a mess you can get into with IFS and functions when you have missed the basics.

https://www.unix.com/shell-programmin...cript-ftp.html

There is no inappropriate use of IFS in that thread.

It is a case of someone not knowing the basics of shell scripting.

@cfajohnson
Agreed. The IFS construct works in many modern shells. Never in dispute - just difficult to follow.

I can write to any local standard, but long experience has shown which constructs are difficult to follow by colleagues and passing contractors.

I too can write obfuscated code which works efficiently but is unmaintainable in a commercial environment.

Sometimes when the data volumes are large and the processing is complex (and I don't have time to write a program) I will use every trick to get a shell script to process the data in the least possible time. The script may be unreadable but it will work.

So vote for the "Clear Code Party" in the next General Election.

(Dismounts high horse and prepares to count both of the votes).

It works in all Bourne-type shells. (And you shouldn't use any other kind for scripts.)

I don't see anything difficult to understand in setting IFS any more than in setting any other variable.

There's nothing obfuscated about setting IFS, especially before a read statement, where it is standard practice.

That's when you should be using awk.

We are in different time zones, and I am getting tired, and with apologies to the O/P for hijacking the post:

I fully agree that the Bourne shell is a sound base for writing portable shell scripts. I do not agree that interfering with IFS is sensible in all common shells.


I must argue this point. It is obfuscated and it is not standard practice. I have scanned thousands of manufacture standard issue scripts and not found one case.


I choose the language to match the specification. There are occasions when awk will do the job, there are occasions when it is just too slow or awkward. I treat awk as a programming language rather than a shell command.

No, it's not. The POSIX shell (a Bourne-type shell) is the sound base for writing portable shell scripts. The Bourne shell is obsolete.

I don't know what you consider standard, but I have found it to be common practice everywhere.

In fact, the bash man page says,

Code:

 IFS   The Internal Field Separator that is used ... to split lines into
       words with the read builtin command.

awk is slow if you use it to process strings; it is much faster than the shell when processing files (anything but a fairly short file, that is).

@cfajohnson
I have enjoyed this debate and look forward to many more. Our ripostes have been founded on logic and deep experience. With unix there is never one set solution to a problem.
bonsoir