Do shell script with SED

Question

I've used this a lot and have never observed this behavior; if it's normal I must really not have been paying attention.
If I have a file (/Q.txt) which contains
cnow
cis the time
cto call
and do this: do shell script "sed 's/c//' < /Q.txt"
the result is
now
is the time
to call
which is what I would expect.
HOWEVER, if use this approach:
set T to "cnow
cis the time
cto call"
do shell script "echo " & quoted form of T & "| sed 's/c//'"
the result is
now
cis the time
cto call
(I can't use the global form, as that will remove other instances of "c")
The only way I can think this will happen is if "echo" removes the returns from T; but looking at the output of echo by itself the result looks okay. And the paragraph count of that result is the same as for T.
What dumb thing am I doing now?

Answer 1

Your issue is with the newlines (or other invisible characters) that are getting used. When I copied your example script, it worked as expected (the first match is replaced on each line). I don't know why the Script Editor would use different newline characters, but you can see from the following example how SED works with various ones:
<pre style="
font-family: Monaco, 'Courier New', Courier, monospace;
font-size: 10px;
margin: 0px;
padding: 5px;
border: 1px solid #000000;
width: 720px;
color: #000000;
background-color: #FFDDFF;
overflow: auto;"
title="this text can be pasted into the Script Editor">
-- use a FF as the newline
set T to "cnowc" & (ASCII character 10) & "cis the timec" & (ASCII character 10) & "cto callc"
do shell script "echo " & quoted form of T & "| sed 's/c//'"
--> correct
-- use a CR as the newline (same as 'return')
set T to "cnowc" & (ASCII character 13) & "cis the timec" & (ASCII character 13) & "cto callc"
do shell script "echo " & quoted form of T & "| sed 's/c//'"
--> same as your result
-- the 'backslash-n' is a newline character that gets converted at compile time
set T to "cnowc\ncis the timec\ncto callc"
do shell script "echo " & quoted form of T & "| sed 's/c//'"
--> correct
-- replace all
set T to "cnowc\ncis the timec\ncto callc"
do shell script "echo " & quoted form of T & "| sed 's/c//g'"
</pre>
Since I can't see what you are using to generate the newlines (but they look the same), I am guessing that the wrong newline is getting placed in there. Copying from various sources may wind up with the different newline characters.
Message was edited by: red_menace