Unable to filter rows which contain "Is a directory" by SED/AWK - sed

Question

I run the code gives me the following sample data
md5deep find * | awk '{ print $1 }'
A sample of the output
/Users/math/Documents/Articles/Number theory: Is a directory
258fe6853b1bfb2d07f512ff6bec52b1
/Users/math/Documents/Articles/Probability and statistics: Is a directory
4811bfb2ad04b9f4318049c01ebb52ef
8aae4ac3694658cf90005dbdea37b4d5
258fe6853b1bfb2d07f512ff6bec52b1
I have tried to filter the rows which contain Is a directory by SED unsuccessfully
md5deep find * | awk '{ print $1 }' | sed s/\/*//g
Its sample output is
/Users/math/Documents/Articles/Number theory: Is a directory
/Users/math/Documents/Articles/Topology: Is a directory
/Users/math/Documents/Articles/useful: Is a directory
How can I filter Out each row which contains "Is a directory" by SED/AWK?
[clarification]
I want to filter out the rows which contain Is a directory.

Answer 1

I have not used the md5deep tool, but I believe those lines are error messages; they would be going to standard error instead of standard out, and so they are going directly to your terminal instead of through the pipe. Thus, they won't be filtered by your sed command. You could filter them by merging your standard error and standard output streams, but
It looks like (I'm not sure because you are missing the backquotes) you are trying to call
md5deep `find *`
and find is returning all of the files and directories.
Some notes on what you might want to do:
It looks like md5deep has a -r for "recursive" option. So, you may want to try:
md5deep -r *
instead of the find command.
If you do wish to use a find command, you can limit it to only files using -type f, instead of files and directories. Also, you don't need to pass * into a find command (which may confuse find if there are files that have names that looks like the options that find understands); passing in . will search recursively through the current directory.
find . -type f
In sed if you wish to use slashes in your pattern, it can be a pain to quote them correctly with \. You can instead choose a different character to delimit your regular expression; sed will use the first character after the s command as a delimiter. Your pattern is also lacking a .; in regular expressions, to indicate one instance of any character you use ., and to indicate "zero or more of the preceding expression" you use *, so .* indicates "zero or more of any character" (this is different from glob patterns, in which * alone means "zero or more of any character").
sed "s|/.*||g"
If you really do want to be including your standard error stream in your standard output, so it will pass through the pipe, then you can run:
md5deep `find *` 2>&1 | awk ...
If you just want to ignore stderr, you can redirect that to /dev/null, which is a special file that just discards anything that goes into it:
md5deep `find *` 2>/dev/null | awk ...
In summary, I think the command below will help you with your immediate problem, and the other suggestions listed above may help you if I did not undersand what you were looking for:
md5deep -r * | awk '{ print $1 }'

Answer 2

To specifically answer the clarification: how to filter out lines using awk and sed:
awk '/Is a directory/ {next} {print}'
sed 'g/Is a directory/d'

Answer 3

Why not use grep instead?
ie,
md5deep find * | grep "Is a directory" | awk '{ print $1 }'
Edit: I just re-read your question and if you want to remove the lines with Is a directory, use the -v flag of grep, ie:
md5deep find * | grep -v "Is a directory" | awk '{ print $1 }'

Answer 4

I'm not intimately familiar with md5deep, but this may do something like you are tying to do.
find -type f -exec md5sum {} +