Left side of pipe is the subshell?
From the bash man page: "Each command in a pipeline is executed as a separate process (i.e., in a subshell)." I suppose it would be possible to execute one component of a pipeline in the current shell (i.e. the first, or the last, or maybe one in the middle), it doesn't play favorites like this: they all execute in subshells. If you modify your script like this:
#!/bin/bashdeclare -i i=0function f1(){ let i++ echo "In f1, SUBSHELL: $BASH_SUBSHELL, i=$i" >&2}f1f1 | f1 | f1echo "at end, i=$i"it prints:
In f1, SUBSHELL: 0, i=1In f1, SUBSHELL: 1, i=2In f1, SUBSHELL: 1, i=2In f1, SUBSHELL: 1, i=2at end, i=1because all 3 invocations of f1 in the pipeline run in subshells.