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On how to select the right tool for a given task


 
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# 1  
Old 10-16-2008
On how to select the right tool for a given task

edit by bakunin: I have split the thread to reflect the two different themes it had. Read the original thread here. All the other posts there dealing with the new theme have been moved here, the ones which addressed both i have copied and edited. Enjoy the discussion.

BTW, you don't want to use sed to work on a string.

Use sed for working on files and shell parameter expansion for manipulating strings.

Last edited by bakunin; 10-18-2008 at 07:47 AM..
# 2  
Old 10-16-2008
Quote:
Originally Posted by cfajohnson

BTW, you don't want to use sed to work on a string.

Use sed for working on files and shell parameter expansion for manipulating strings.
[/INDENT]
its perfectly all right to use sed on strings(as well as files of course).
# 3  
Old 10-16-2008
Quote:
Originally Posted by ghostdog74
its perfectly all right to use sed on strings(as well as files of course).

It is wasteful (in terms of both time and resources) to use an external program to do something that the shell can do internally.
# 4  
Old 10-17-2008
Quote:
Originally Posted by cfajohnson

It is wasteful (in terms of both time and resources) to use an external program to do something that the shell can do internally.
i understand where you are coming from. but there are few situations i can think of that using shell provided internals are not suitable
1) writing portable scripts. The syntax that you use for string manipulations in bash for example, is not universal for every shell
2) doing more complex string manipulation like grouped pattern matches.
3) and of course, using sed to go over files can be faster than using pure shell constructs.
# 5  
Old 10-17-2008
Quote:
Originally Posted by ghostdog74
i understand where you are coming from. but there are few situations i can think of that using shell provided internals are not suitable
1) writing portable scripts. The syntax that you use for string manipulations in bash for example, is not universal for every shell

The techniques I used are part of the standard UNIX shell.

They are portable to all modern *nix systems (and many older ones).

I used nothing that is bash specific.
Quote:
2) doing more complex string manipulation like grouped pattern matches.

When a regular expression, rather than wildcard expansion is necessary, then sed might be appropriate (though I would usually prefer awk).
Quote:
3) and of course, using sed to go over files can be faster than using pure shell constructs.

As I said, sed is for working with files.
# 6  
Old 10-17-2008
Quote:
Originally Posted by cfajohnson
They are portable to all modern *nix systems (and many older ones).
older ones like bourne (Solaris) will break. I have not tried csh, but i think it will break too.

Quote:
though I would usually prefer awk).
i prefer awk too.

Quote:
As I said, sed is for working with files.
and strings...
# 7  
Old 10-17-2008
Quote:
Originally Posted by ghostdog74
older ones like bourne (Solaris) will break.

On Solaris, /bin/sh is not a POSIX shell, but there is always one installed. It may be /usr/pkg4/bin/sh, and there is usually ksh and possibly bash.
Quote:
I have not tried csh, but i think it will break too.

csh is not the standard Unix shell, and it will not run standard shell scripts, even old-style Bourne scripts; it is a different language and not recommended for scripting.

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