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I am uploading a file via sftp and just performing the safety test if the file is completely uploaded to the remote server. I am taking md5 hash of both(file in local and file in remote server) and matching them. If they match I conclude that the upload was successful. Here is the part of code from shell script.

ssh $REMOTE_MC 'digest -a md5 $TARGET_DIR/$filename' > $HOME_DIR/remote_hash_$datetag.txt
local_hash=$(md5sum $HOME_DIR/$dump | cut -d' ' -f1)
echo "local = $local_hash"
cat $HOME_DIR/remote_hash_$datetag.txt
remote_hash=$(cat $HOME_DIR/remote_hash_$datetag.txt)
echo "remote = $remote_hash" 



output:
local = cd8d77f0467754bc0c1c7ac3fb7f6184
dee4a8484f99c577fd70cb8fa01e5995
remote = dee4a8484f99c577fd70cb8fa01e5995

The problem I am facing is that,when i run the script, hashes differ but if I run the command
ssh $REMOTE_MC 'digest -a md5 $TARGET_DIR/$filename' > $HOME_DIR/remote_hash_$datetag.txt
out of the shell script, i get the same hash. What am i doing wrong in the script?

Things I tried:
ssh $REMOTE_MC 'digest -a md5 $TARGET_DIR/$filename >> $TARGET_DIR/remote.txt'
I redirected the output to a remote file instead of local file, the remote file contains the correct hash. But if i redirect it to local file, the hash mismatches.

Thanks in advance.

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You are using single quotes surrounding the ssh command. This way the variables $TARGET_DIR and $filename are taken literally instead of being evaluated. Change the single quotes to double quotes to have the variables evaluated:

ssh $REMOTE_MC "digest -a md5 $TARGET_DIR/$filename" > $HOME_DIR/remote_hash_$datetag.txt

Another suggestion is to write the variables as ${variable} like ${datetag} to make the variable name boundaries more clear.

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