Revisions to Output tee to stdout while writing to a FD using here-strings

replace tag fd with file-descriptors

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edit approved Nov 9, 2020 at 15:55

thanasisp

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edited Jul 24, 2020 at 16:37

kon

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EDIT: Please refer to @Stéphane Chazelas answer. My updates below may be true but way to complicated.

Update: I am getting closer I guess. When trying tee <<< "Output this to stdout" >(tee -a >&4) I can actually see the output in my terminal and it writes to the file but for some reason it overrides the content and doesn´t seem to append (-a).

EDIT: Please refer to @Stéphane Chazelas answer. My updates below may be true but way to complicated.

Update: I am getting closer I guess. When trying tee <<< "Output this to stdout" >(tee -a >&4) I can actually see the output in my terminal and it writes to the file but for some reason it overrides the content and doesn´t seem to append (-a).

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edited Jul 24, 2020 at 15:47

kon

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5

Update:Update: I am getting closer I guess. When trying tee <<< "Output this to stdout" >(tee -a >&4) I can actually see the output in my terminal and it writes to the file but for some reason it overrides the content and doesn´t seem to append (-a).

Update 2:Update 2: I feel like I´ve found my mistake now.

exec 4<>"/tmp/testfile.txt"; # open FD 4 read (<) and write (>) cat <&4;<&4 >/dev/null; tee >(tee -a >&4) <<< "Output this to stdout" # read fd (>/dev/null to silent the output) for correct position and append to. Also output to stdout exec 4>&- # close FD (this closes it completly, so no need for exec 4<&-)

Update: I am getting closer I guess. When trying tee <<< "Output this to stdout" >(tee -a >&4) I can actually see the output in my terminal and it writes to the file but for some reason it overrides the content and doesn´t seem to append (-a).

Update 2: I feel like I´ve found my mistake now.

exec 4<>"/tmp/testfile.txt"; # open FD 4 read (<) and write (>) cat <&4; tee >(tee -a >&4) <<< "Output this to stdout" # read fd for correct position and append to. Also output to stdout exec 4>&- # close FD (this closes it completly, so no need for exec 4<&-)

Update: I am getting closer I guess. When trying tee <<< "Output this to stdout" >(tee -a >&4) I can actually see the output in my terminal and it writes to the file but for some reason it overrides the content and doesn´t seem to append (-a).

Update 2: I feel like I´ve found my mistake now.

exec 4<>"/tmp/testfile.txt"; # open FD 4 read (<) and write (>) cat <&4 >/dev/null; tee >(tee -a >&4) <<< "Output this to stdout" # read fd (>/dev/null to silent the output) for correct position and append to. Also output to stdout exec 4>&- # close FD (this closes it completly, so no need for exec 4<&-)