Foss User ha scritto:
I see that the read command stores input entered only on the console
into the variables. Example:
$ read a
foo
$ echo $a
foo
But when I don't enter input on the console by keyboard, but pipe it
into the standard input of read, I am unable to store the input into
the variable.
$ echo bar | read a
$ echo $a
foo
However, the help of read says this:
$ help read
read: read [-ers] [-a array] [-d delim] [-i text] [-n nchars] [-p
prompt] [-t timeout] [-u fd] [name ...]
Read a line from the standard input and split it into fields.
So, why is it not reading the line from standard input when input is
passed to it using a pipe?
Because the "read" is done in a child process, that starts, executes its
instructions (ie: read), modifies its own private environment, and then
dies, leaving the parent's environment untouched.
Try:
$echo qwerty | while read a ; do echo "a=$a" ; done
a=qwerty
$echo "a=$a"
a=
Hope that helped
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