Shell scripting input redirection oddities *

Question

Can anyone explain this behavior? Running:

#!/bin/sh
echo "hello world" | read var1 var2
echo $var1
echo $var2

results in nothing being ouput, while:

#!/bin/sh
echo "hello world" > test.file
read var1 var2 < test.file
echo $var1
echo $var2

produces the expected output:

hello
world

Shouldn't the pipe do in one step what the redirection to test.file did in the second example? I tried the same code with both the dash and bash shells and got the same behavior from both of them.

Answer

A recent addition to bash is the lastpipe option, which allows the last command in a pipeline to run in the current shell, not a subshell, when job control is deactivated.

#!/bin/bash
set +m      # Deactiveate job control
shopt -s lastpipe
echo "hello world" | read var1 var2
echo $var1
echo $var2

will indeed output

hello
world

< br > via < a class="StackLink" href=" http://stackoverflow.com/questions/2732/" >Shell scripting input redirection oddities< /a>

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