Designating literal characters in "do shell script"

Question

(Also posted in UNIX forum)
If, in Terminal, I do this:
echo 1/2/3 | sed 's/\/2\// and /g'
I get the expected result, which is:
1 and 3
But if, in AS, I do this:
do shell script "echo 1/2/3 | sed 's/\/2\// and /g'"
I get this error message:
Expected “"” but found unknown token.
If I change the AS command to:
do shell script "echo 1/2/3 | sed 's//2/ and /g'"
I get this error message:
sed: 1: "s//2// and /g": bad flag in substitute command: '/'
(Of course, if I change the AS command to:
do shell script "echo 1/2/3 | sed 's/2/ and /g'"
I get the expected result, which is:
1/ and /3
but this is no help in getting rid of the forward slashes, which is what I want.)
I think this also happens with some other "special" characters surrounding "2". A Google search would seem to indicate this as a well-known dilemma, but I haven't stumbled across a clear solution -- is there one?

Answer 1

osimp,
I also replied in the Unix forum. But here's a little more explanation.
Your command string gets "evaluated" twice... first by AppleScript and then by the shell. Since backslash characters are escape characters in both AppleScript and the shell, you want literal backslashes passed from AppleScript to the shell so when the shell gets the command string it will process them as escape characters in front of the forward slashes.
So you need to escape the backslashes (double-backslash) in AppleScript so they'll be passed to the shell as literal backslashes (single-backslash). Then when the shell evaluates the string the single-backslashes will be treated as escape characters.
<pre>
do shell script "echo 1/2/3 | sed 's/\\/2\\// and /g'"
</pre>
Steve