[RndTbl] *reading* a file causes reboot

Adam Thompson athompso at athompso.net
Tue May 5 07:43:58 CDT 2015


Oh dear.  Yeah, that would definitely do it.

The shell won't expand the second alias because it's an argument, not a command, from the shell's perspective.
In bash et al., you might be able to do "alias1 ( alias2 )".  No clue about tcsh.

Checking the man pages, bash accommodates this if the final character of the alias is a space (!) but I don't see anything similar for tcsh.
Using a shell function in bash instead of an alias would also enable the desired behavior, maybe that would work in tcsh, too?

-Adam

On May 5, 2015 1:08:10 AM CDT, Trevor Cordes <trevor at tecnopolis.ca> wrote:
>The plot thickens...
>
>I double-checked the exact command I was running when I did the grep...
>
>I ran:
>
>n19 grep -r foobar /
>
>n19 is an alias I've been using forever (and as per last month's RTFM):
>/bin/nice -19 /usr/bin/ionice -c2 -n7 -t
>
>I n19 almost everything long-lasting / non-interactive I run.
>
>It just dawned on me: "nah, the shell (tcsh) couldn't be expanding the
>n19 alias and *not* expanding the grep alias, could it?"
>
>Sure enough, after a few tests, it is clear the shell only expands the
>first alias on the line.  So that means (tada) my grep -r wasn't being
>run with the --devices option!  That is why it was opening the device
>files.  In my quest to be "nice", I shot myself in the foot.
>
>So now the question is why doesn't the shell expand both aliases (I
>guess it's a safety / can't-tell-what-you-mean issue); is there a way
>to make the n19 alias expand the command listed after it too; or can I
>tell the shell to expand aliases after "modifier" commands (nice,
>xargs,
>etc).
>
>Nice test case (may have to be modified for bash):
>
>#alias n19	'/bin/nice -19 /usr/bin/ionice -c2 -n7 -t'
>
>#nice n19 echo bobo
>/bin/nice: n19: No such file or directory
>
>#n19 n19 echo bobo
>ionice: failed to execute n19: No such file or directory
>
>In a perfect world the system would "do what I mean" and both above
>commands would succeed, just as this does:
>
>nice nice echo bobo
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