While loop, input from find command


 
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# 1  
While loop, input from find command

Hello nix Experts,

I am a *nix rookie and have run into this issue, can some one help me here and let me know what I am doing wrong.

Code:
/home/user1> while read n
> do
> echo $n
> done < <(find . -type f -ctime -1 | grep abc)

I am getting the below error:
-sh: syntax error near unexpected token `<'

When I do a shell check to see what Shell I am using by default, i get this:
Code:
/home/user1>which shell
/usr/bin/which: no shell in (/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin:/opt/ibm/director/bin)

Any suggestion is greatly appreciated.
# 2  
Try echo $SHELL to find your shell. Or just ps. "which shell" looks for a command named shell, which isn't much help.

How about this, with -name to avoid the grep. This checks in the filename. -path would check in the file path instead.

Code:
find . -type f -ctime -1 -name '*abc*' | while IFS="" read -r FILE
do
        echo "$FILE"
done



The IFS avoids having read split on anything, and the -r prevents it from trying to evaluate backslashes. It's a good habit when you want read to give you literal, unchanged input...

One caveat: Variables you set inside the "while" won't be set outside the loop. The | puts the loop into a separate, independent subshell.
This User Gave Thanks to Corona688 For This Post:
# 3  
Quote:
Originally Posted by Corona688
One caveat: Variables you set inside the "while" won't be set outside the loop. The | puts the loop into a separate, independent subshell.
Depends on the shell.. Smilie
Code:
$
$ cat kshlooptest
#! /bin/ksh
LAST="nothing"
find /etc -name 'w*' 2> /dev/null | while IFS="" read name ; do
        LAST=$name
done
echo outside of while loop LAST = $LAST
exit 0
$
$
$ ./kshlooptest
outside of while loop LAST = /etc/gconf/schemas/window-list.schemas
$

# 4  
Quote:
Originally Posted by Perderabo
Depends on the shell.. Smilie
Yes, I know. ksh yes, absolutely-anything-other-than-ksh no.

This cuts both ways incidentally. It's possible for ksh to break a script from variables behind a pipe having a different scope than specified by POSIX.
# 5  
Thanks for the reply guys, that was helpful
# 6  
The current standard says:
Quote:
A subshell environment shall be created as a duplicate of the shell environment, except that signal traps that are not being ignored shall be set to the default action. Changes made to the subshell environment shall not affect the shell environment. Command substitution, commands that are grouped with parentheses, and asynchronous lists shall be executed in a subshell environment. Additionally, each command of a multi-command pipeline is in a subshell environment; as an extension, however, any or all commands in a pipeline may be executed in the current environment. All other commands shall be executed in the current shell environment.
So, variable assignments in a while loop in a pipeline are allowed, but not required, to be visible in the current shell execution environment after the pipeline terminates.

The last element of a pipeline is run in the current shell execution environment in ksh.
The last element of a pipeline is run in a subshell environment in bash.
On this point, both are OK according to the standard.
 

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