Re: Using << and an output pipe together in shell (bash)

On 2024-10-31, Kenny McCormack <gazelle@shell.xmission.com> wrote:

In article <87r07v99wd.fsf@bsb.me.uk>, Ben Bacarisse  <ben@bsb.me.uk> wrote:
...

I think you need "| \" at the end of this line.  At least that's what I
usually do and it seems to work.

>
It is not generally necessary to put a backslash at the end of a line that
ends with | (in shell script).

The << feature works outside of the ordinary shell grammar, fetching
data in a line-oriented way until the delimiter.

If you have multiple occurrences, both their data parts go after
the command:

cmd1 << EOF | cmd2 << EOF | cmd3 << EOF
data1
EOF
data2
EOF
data3
EOF

Actual run with && rather than |:

$ cat << EOF && cat << EOF && cat << EOF

foo
EOF
bar
EOF
xyzzy
EOF

foo
bar
xyzzy

It looks like the implementation of << pulls logical lines (after
backslash folding) during parsing.

If this entire command pipe were parsed first:

  cmd1 << EOF | cmd2 << EOF | cmd3 << EOF

and then a second pass took place to fetch the EOF-delimited pieces of
syntax that it requires, then it could contain artbitrary backslahes.


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