Ferguson, Neale writes: > Strange situation: > > #!/bin/sh > a="1.2.3" > echo "a="$a > b=`echo $a | tr -d "."` > echo "b="$b > echo $a | tr -d "." | read -e c > echo "c="$c > > I'd expect: > > a=1.2.3 > b=123 > c=123 > > but I get: > > a=1.2.3 > b=123 > c= > > The builtin function "read" is supposed to read from standard > input which should be the output stage of the pipe. It works > the same on Linux 86 but AIX & HP return the expected results. > > Any ideas?
It's because the "read" is getting executed in a separate process. Excerpting from http://www.faqs.org/faqs/unix-faq/faq/part3/section-8.html Right, take the next example: foo=bar echo bletch | read foo echo "foo is now: $foo" This will print ``foo is now: bar'' in many implementations, ``foo is now: bletch'' in some others. Why? Generally each part of a pipeline is run in a different subshell; in some implementations though, the last command in the pipeline is made an exception: if it is a builtin command like ``read'', the current shell will execute it, else another subshell is created. POSIX 1003.2 allows both behaviours so portable scripts cannot depend on any of them. --Malcolm -- Malcolm Beattie <[EMAIL PROTECTED]> Linux Technical Consultant IBM EMEA Enterprise Server Group... ...from home, speaking only for myself
