Subj : Re: Running a command dynamically in a script
To   : comp.os.linux
From : steve_roach
Date : Fri Jul 09 2004 09:35 pm

Sybren Stuvel <sybrenUSE@YOURthirdtower.imagination.com> wrote in message news:<slrncesh8c.teg.sybrenUSE@sybren.thirdtower.com>...
> steve enlightened us with:
> > - 'ps' executes but does not redirect the output to a_file
> > - Quite possibly because of this, when a_file can't be written to
> > (maybe the
> >   target directory is owned by someone else), the status is 0 when it,
> > in
> >   fact, failed.
> 
> $ help eval
> 
> Sybren

Right on the money, Sybren. And just to prove it:

-------------------------------------------------------------------------
[dev]$ ls -l
total 24
-rwxr--r--    1 steve    dev           610 Jul 10 13:29 go
-rw-r--r--    1 steve    dev            36 Jul 10 13:25 source
-rw-r--r--    1 steve    dev             0 Jul 10 13:30 tmp.log
[dev]$ cat source
1,ps > tmp.log
2,ps > /root/tmp.log
[dev]$ cat go

# Clear the log.
rm -f tmp.log

# Get a command that works
call_text=`grep 1 source | cut -d',' -f2`

# Show us the command
echo "Command: $call_text"

# Execute the command
eval $call_text

# See how it did
status=$?

# Did the redirect work?
cat tmp.log

# And tell us about it
echo "This should be 0: $status"

# Get a command that doesn't work
call_text=`grep 2 source | cut -d',' -f2`

# Show us the command
echo "Command: $call_text"

# Execute the command
eval $call_text

# See how it did
status=$?

# Did the redirect work?
cat /root/tmp.log

# And tell us about it
echo "This should be 1: $status"

[dev]$ ./go
Command: ps > tmp.log
  PID TTY          TIME CMD
19227 pts/0    00:00:00 bash
20869 pts/0    00:00:00 bash
20874 pts/0    00:00:00 ps
This should be 0: 0
Command: ps > /root/tmp.log
../go: /root/tmp.log: Permission denied
cat: /root/tmp.log: Permission denied
This should be 1: 1
---------------------------------------------------------------------

BTW, good sig.

.