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Bash The output of the command "wc -l" is different if the call or through a tee

When I issued two equivalent commands in Bash, I got a different output (from the "wc -l" command), see below:

root@devel:~# ls /usr/bin -lha | tee >(wc -l) >(head) > /dev/null
total 76M
drwxr-xr-x  2 root root      20K Nov 11 18:58 .
drwxr-xr-x 10 root root     4.0K Oct  8 15:31 ..
-rwxr-xr-x  1 root root      51K Feb 22  2017 [
-rwxr-xr-x  1 root root       96 Jan 19  2017 2to3-3.5
-rwxr-xr-x  1 root root      23K Mar 22  2017 addpart
lrwxrwxrwx  1 root root       26 May 10  2017 addr2line -> x86_64-linux-gnu-    addr2line
lrwxrwxrwx  1 root root        6 Dec 13  2016 apropos -> whatis
-rwxr-xr-x  1 root root      15K Sep 13 19:47 apt
-rwxr-xr-x  1 root root      79K Sep 13 19:47 apt-cache
137
root@devel:~# ls /usr/bin -lha | wc -l
648

What am I missing?

This is strange, but when I call it that way, it gets an even stranger result:

root@devel:~# ls /usr/bin -lha | tee >(wc) >(wc) > /dev/null
648    6121   39179
648    6121   39179
root@devel:~# ls /usr/bin -lha | tee >(wc) >(wc) > /dev/null
648    6121   39179
648    6121   39179
root@devel:~# ls /usr/bin -lha | tee >(wc) >(wc -l) > /dev/null
648
root@devel:~#     648    6121   39179

it seems that the commands are executed asynchronously and end at different times ... or what could it be?

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1 answer

Simple answer:

how to fix:

ls /usr/bin -lha | tee --output-error=exit-nopipe >(wc -l) >(head) > /dev/null

Details:

The command headprints only the input header, so it can complete its task until it receives enough input, and then exits without waiting for all the data to be entered.

, head "head".

ls /usr/bin -lha | tee >(wc -l) >(read l; echo $l) > /dev/null

"head" , , pipe , tee .

, , "head". wc - .

, , , tee , tee , .

, , .

MODE determines behavior with write errors on the outputs:
   'warn' diagnose errors writing to any output

   'warn-nopipe'
          diagnose errors writing to any output not a pipe

   'exit' exit on error writing to any output

   'exit-nopipe'
          exit on error writing to any output not a pipe

   The  default MODE for the -p option is 'warn-nopipe'.  The default operation
   when --output-error is not specified, is to exit immediately on error writing to
   a pipe, and diagnose errors writing to non pipe outputs.

, <(wc -l) , , 16384 20480, 4096.

4096 - PIPE_BUF UNIX. , PIPE_BUF, , 4096.

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