Why is it needed to use file-descriptors for returning UDP or TCP traffic in bash? -


i aware 1 needs use file-descriptors in order read tcp or udp sockets. example:

exec 3<>/dev/udp/192.0.2.1/161; echo -n "302902010104067075626c6963a01c02047f14ec98020100020100300e300c06082b060102010105000500" | xxd -r -p >&3; read -n 1 -t 0.2 <&3

however, why isn't possible read sockets directly, e.g:

echo -n "302902010104067075626c6963a01c02047f14ec98020100020100300e300c06082b060102010105000500" | xxd -r -p > /dev/udp/192.0.2.1/161; read -n 1 -t 0.2 < /dev/udp/192.0.2.1/161

a socket single file descriptor can used in 2 directions. usual file operators in bash, < , > work on 1 file descriptor in 1 direction.

you overwrite existing descriptor, stdin, , use file descriptor number explicitly. equivalent using separate descriptor.


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