I have a here document inside a bash script. I want to read a value from it like that :
su myUser<<SESSION
set -x
echo -n "Enter your name and press [ENTER]: "
read name
echo "the name is $name"
SESSION
But when I launch this script from another user, bash does not stop himself to wait for an input and ignore the read command.
Any ideas ?
As L. Scott Johnson correctly found, the read reads from standard input. The standard input in the shell that su runs is connected to the here-document, so the read reads the literal string echo "the name is " (note that since the here-document is unquoted, the $name has already been expanded to an empty string, or to whatever value it had in the calling shell).
Here is the same thing, but with a quoted here-document, and an extra line outputting $name again:
su username <<'SESSION'
set -x
echo -n "Enter your name and press [ENTER]: "
read name
echo "the name is $name"
echo "What I read was $name"
SESSION
The output would be
Password:
+ echo -n Enter your name and press [ENTER]:
Enter your name and press [ENTER]: + read name
+ echo What I read was echo "the name is $name"
What I read was echo "the name is $name"
To correctly do this, you can't have read reading from standard input. Instead, open a new file descriptor as a copy of standard input, and get read to read from that:
su username 3<&0 <<'SESSION'
set -x
echo -n "Enter your name and press [ENTER]: "
read name <&3
echo "the name is $name"
SESSION
If the shell of the other user is bash or ksh, then read name <&3 may be replaced by read -u3 name.
Note however that you can't expect the name variable to be set in the shell calling su as a child shell can't modify the environment (variables etc.) of a parent shell.
ssh to do a few things on the remote host, possibly processing the data locally.
It doesn't ignore the read command; it executes it and reads stdin. Then the line echo "the name is $name is read (from stdin) and assigned to $name.
su myUser<<SESSION
set -x
echo -n \"Enter your name and press [ENTER]: \"
read name
someUser
echo \"the name is \$name\"
SESSION
output:
+ echo -n '"Enter' your name and press '[ENTER]:' '"'
-n "Enter your name and press [ENTER]: "
+ read name
+ echo '"the' name is 'someUser"'
"the name is someUser"
