bash: How to: read -d '\r' . . (delimit on a meta character)

Howard_L · #1 07-Oct-2009, 09:14

Hi again , How about this one:
I am writing a script to talk to my pop server.
All the lines returned from the server are crlf (0x0d 0x0a)
The read command trims the 0x0a and the line is left with 0x0d ending.
I figured out how to use the tr utility do delete it:

Code:

~>  s=abcdex; s=$(echo $s | tr x '\r'); echo -n $s > xf1; hexdump -C xf1;
00000000  61 62 63 64 65 0d                                 |abcde.|
00000006
~>  s=$(echo $s | tr -d '\r'); echo -n $s > xf1; hexdump -C xf1;
00000000  61 62 63 64 65                                    |abcde|
00000005

Which is cool , but it be even better to just stop reading there.
So I have not been able to figure out how to get read to see the \r.
examples:

Code:

~>  s=abcdexyz; s=$(echo $s | tr x '\r'); echo -n $s > xf1; hexdump -C xf1;
00000000  61 62 63 64 65 0d 79 7a                           |abcde.yz|
00000008

# So there is an 0x0d , Now use read -d on a regular character:

~>  read -d e < "xf1"; echo "$REPLY"
abcd

# But I can't seem to figure out how to get read to id the 0x0d:

~>  read -d \r < "xf1"; echo "$REPLY"
yzcde
~>  read -d '\r' < "xf1"; echo "$REPLY"
yzcde
~>  read -d '\\r' < "xf1"; echo "$REPLY"
yzcde
~>  read -d \\r < "xf1"; echo "$REPLY"
yzcde
~>  read -d 0x0d < "xf1"; echo "$REPLY"
yzcde

Why is tr able to id the '\r' and bash read not? (because it was designed to?)
Is this where I need to learn to use RE in bash?

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