[PD] [command] can't execute "ls | wc -l"

IOhannes m zmoelnig zmoelnig at iem.at
Wed Jun 8 11:17:08 CEST 2022

On 6/8/22 09:43, Alexandros wrote:
> While [ggee/shell] outputs the correct number of files in a directory 
> with the message "ls | wc -l", [command] outputs an error code 2 with 
> "exec ls | wc -l" and doesn't output anything.
> Is this intentional? If so, how can this command be executed by [command]?

probably by chaining up multiple [command]s?

but more importantly: "ls | wc -l" is an anti-pattern: you shouldn't 
parse the output of `ls` [1]
e.g. your script breaks as soon as your directory contains files with a 
newline in their name.

a safer way would be to run
 > find * -maxdepth 0 -type f  -exec printf . ";" | wc -c

but this is absymally slow (and still has the problem with the pipe).

a faster way would be to run this simple shell-script:
for f in *; do
echo $i

you can run this by creating a single symbol (without the quotes)
"i=0; for f in *; do i=$((i+1)); done; echo $i"

and then send a message "exec bash -c $1" (with $1 replaced by the 
symbol) to [command].
this will launch a full-fledged bash that will then interpret your 
little script.

an even better way would be to just use [file glob]


[1] http://mywiki.wooledge.org/ParsingLs
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