Bash: Check if remote directory exists using FTP - bash

Question

I'm writing a bash script to send files from a linux server to a remote Windows FTP server.
I would like to check using FTP if the folder where the file will be stored exists before attempting to create it.
Please note that I cannot use SSH nor SCP and I cannot install new scripts on the linux server. Also, for performance issues, I would prefer if checking and creating the folders is done using only one FTP connection.
Here's the function to send the file:
sendFile() {
ftp -n $FTP_HOST <<! >> ${LOCAL_LOG}
quote USER ${FTP_USER}
quote PASS ${FTP_PASS}
binary
$(ftp_mkdir_loop "$FTP_PATH")
put ${FILE_PATH} ${FTP_PATH}/${FILENAME}
bye
!
}
And here's what ftp_mkdir_loop looks like:
ftp_mkdir_loop() {
local r
local a
r="$#"
while [[ "$r" != "$a" ]]; do
a=${r%%/*}
echo "mkdir $a"
echo "cd $a"
r=${r#*/}
done
}
The ftp_mkdir_loop function helps in creating all the folders in $FTP_PATH (Since I cannot do mkdir -p $FTP_PATH through FTP).
Overall my script works but is not "clean"; this is what I'm getting in my log file after the execution of the script (yes, $FTP_PATH is composed of 5 existing directories):
(directory-name) Cannot create a file when that file already exists.
Cannot create a file when that file already exists.
Cannot create a file when that file already exists.
Cannot create a file when that file already exists.
Cannot create a file when that file already exists.

Answer 1

To solve this, do as follows:
To ensure that you only use one FTP connection, you create the input (FTP commands) as an output of a shell script
E.g.
$ cat a.sh
cd /home/test1
mkdir /home/test1/test2
$ ./a.sh | ftp $Your_login_and_server > /your/log 2>&1
To allow the FTP to test if a directory exists, you use the fact that "DIR" command has an option to write to file
# ...continuing a.sh
# In a loop, $CURRENT_DIR is the next subdirectory to check-or-create
echo "DIR $CURRENT_DIR $local_output_file"
sleep 5 # to leave time for the file to be created
if (! -s $local_output_file)
then
echo "mkdir $CURRENT_DIR"
endif
Please note that "-s" test is not necessarily correct - I don't have acccess to ftp now and don't know what the exact output of running DIR on non-existing directory will be - cold be empty file, could be a specific error. If error, you can grep the error text in $local_output_file
Now, wrap the step #2 into a loop over your individual subdirectories in a.sh

Answer 2

#!/bin/bash
FTP_HOST=prep.ai.mit.edu
FTP_USER=anonymous
FTP_PASS=foobar#example.com
DIRECTORY=/foo # /foo does not exist, /pub exists
LOCAL_LOG=/tmp/foo.log
ERROR="Failed to change directory"
ftp -n $FTP_HOST << EOF | tee -a ${LOCAL_LOG} | grep -q "${ERROR}"
quote USER ${FTP_USER}
quote pass ${FTP_PASS}
cd ${DIRECTORY}
EOF
if [[ "${PIPESTATUS[2]}" -eq 1 ]]; then
echo ${DIRECTORY} exists
else
echo ${DIRECTORY} does not exist
fi
Output:
/foo does not exist
If you want to suppress only the messages in ${LOCAL_LOG}:
ftp -n $FTP_HOST <<! | grep -v "Cannot create a file" >> ${LOCAL_LOG}