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Treat Command Output as a File

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# 8  
Old 10-01-2014
What OS are you on, does your system have /dev/fd/?

If so, you could consider using bash or ksh shells. Basically if the <(command) works your system supports it.

This is not very portable and is typically avoided because of this. However if you know your only going to run the script on known platform(s).
This User Gave Thanks to Chubler_XL For This Post:
aimy
# 9  
Old 10-01-2014
Quote:
Originally Posted by Chubler_XL
What OS are you on, does your system have /dev/fd/?

If so, you could consider using bash or ksh shells. Basically if the <(command) works your system supports it.

This is not very portable and is typically avoided because of this. However if you know your only going to run the script on known platform(s).
Code:
$ cd /dev/fd/
sh: /dev/fd/:  not found.
$ uname -a
HP-UX system1 B.11.31 U ia64 0189138652 unlimited-user license
$ echo $SHELL
/sbin/sh
$

Smilie
# 10  
Old 10-01-2014
echo $0
This User Gave Thanks to vgersh99 For This Post:
aimy
# 11  
Old 10-01-2014
Quote:
Originally Posted by vgersh99
echo $0
Code:
$ echo $0
-sh

---------- Post updated at 01:26 PM ---------- Previous update was at 01:22 PM ----------

I've read somewhere that I can use `! <command> ` for Bourne instead.

But the output is not what I expect. So I just would some clarification here.

Does this BASH shell script
Code:
grep -vxFf incomplete.list <(cut -c 1-25 source.list

equivalent to this BOURNE shell script
Code:
grep -vxFf incomplete.list `! cut -c 1-25 source.list`

Thank you.
# 12  
Old 10-01-2014
For HPUX /sbin/sh is a POSIX-compliant shell. POSIX does not require process substitution, which is what you are asking for. Out of the box 11i HPUX has /bin/ksh which does support it.

This explains it:
Process substitution [Bash Hackers Wiki]

Whether or not it is allowed on a given OS depends on the existence
Code:
 /dev/fd

If you get a return from
Code:
ls /dev/fd

ex:
Code:
$>  ls /dev/fd
0 1 2 3 5 9

then process substitution will work in ksh.

To enable ksh, put a shebang on the first line of a script in the leftmost column:
Code:
#!/bin/ksh

This User Gave Thanks to jim mcnamara For This Post:
aimy
# 13  
Old 10-01-2014
No, it is not. The first, although missing a closing parenthesis, is called "process substitution" and offers cut's results as a stream on stdin for grep.
The second offers cut's results as a list of parameters (i.e. file names) to grep . The "!" will invert cut's exit code in sh, it will perform history expansion in bash.
This User Gave Thanks to RudiC For This Post:
aimy
# 14  
Old 10-01-2014
Thanks Jim & Rudic.

Btw, I just noticed that in reality this code should be the other way around actually:
Code:
cut -c 1-25 source.list | grep -vxFf complete.list

that is I have to find the missing item from source.list against complete.list

So, is it possible without having to create a new file to get the cut -c 1-25 source.list part?

Thanks.

---------- Post updated at 10:26 AM ---------- Previous update was at 09:23 AM ----------

At the moment, I use this command to avoid multiple lines command:
Code:
cut -c 1-25 source.list > source.temp && grep -vxFf source.temp complete.list > missing.list && rm -f source.temp

But the issue here is, the rm -f source.temp is only executed whenever the missing.list is not 0 in size.

Please help.

Thank you.
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