shell script problem: does not work on the terminal, but works in a script

I was playing with shell scripting, when a strange thing happened. I need someone to explain it.

I have a file 'infile', contents:

line one
line2
third line
last

a test script test.sh, contents:

read var1
echo $var1

i executed:

cat infile | ./test.sh

output was

line one

Then I did:

cat infile | read var1
echo $var1

Result: a blank line.

I even tried

c开发者_开发百科at infile | read var1; echo $var1;

same result.

why does this happen?

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The pipe causes the command after it to run in a subshell, which means that environment variables won't be propagated to the main shell. Use redirection or a herestring to get around this:

read var1 < infile

---

Or try this:

cat file | ( read var1; echo $var1; )