First: Create a script. You can call it whatever you want. I will call it
#!/bin/bash PROTOCOL="ftp" URL="server.example.com" LOCALDIR="/home/user/downloads" REMOTEDIR="dir/remote/server/" USER="user" PASS="password" REGEX="*.txt" LOG="/home/user/script.log" cd $LOCALDIR if [ ! $? -eq 0 ]; then echo "$(date "+%d/%m/%Y-%T") Cant cd to $LOCALDIR. Please make sure this local directory is valid" >> $LOG fi lftp $PROTOCOL://$URL <<- DOWNLOAD user $USER "$PASS" cd $REMOTEDIR mget -E $REGEX DOWNLOAD if [ ! $? -eq 0 ]; then echo "$(date "+%d/%m/%Y-%T") Cant download files. Make sure the credentials and server information are correct" >> $LOG fi
Second: Add it to crontab. If you want to execute it every exact 15 minutes inside an hour:
45,30,15,00 * * * * /home/user/downloader.sh >/dev/null 2>&1
If you want to execute it each 15 minutes no matter what is the starting minute:
*/15 * * * * /home/user/downloader.sh >/dev/null 2>&1
Explaining the variables:
PROTOCOL– What protocol to use.
lftpsupports a good range of them:
ftp, ftps, http, https, hftp, fish, sftpand
file. https and ftps require lftp to be compiled with OpenSSL or GNU TLS support.
URL– Name or IP of the server. You can even add
:PORTat the end if your server doesn’t use the default port of the protocol being used.
LOCALDIR– Where to save the files.
REMOTEDIR– Where to
cdon the remote server to get the files.
PASSWORD– ftp credentials.
REGEX– Regular expression to filter files to download. It can be useful if you want to download only files of a determined extension, for example. Use
*if you want to download everything.
LOG– Logfile location.
Explaining some code logic:
1. – if
if [ ! $? -eq 0 ]; then fi
$? variable is a special bash variable that means “status code of last command”. Bash always return zero on successful command executions so, comparing
-eq (equal to) with the starting
!(negative) on an
if should be enough to see if
lftp had issues during execution. If you want a better log of what happened, you will have to crawl through those commands’ documentation.
2. – heredocs
lftp $PROTOCOL://$URL <<- DOWNLOAD DOWNLOAD
bash heredocs. It’s a way to say “feed this command with this input list”. I’ve named the limit string
DOWNLOAD so, everything between
<<- DOWNLOAD and
DOWNLOAD will be input to
lftp. You will see examples on the internet with
<< symbol but I prefer the
<<- version since it supports indentation.
3. – lftp commands
user $USER "$PASS" cd $REMOTEDIR mget -E $REGEX
These are internal commands of
lftp that means respectively, auth the user with
$USER login and
"$PASS" password, change to
$REMOTEDIR and bulk download anything with the
$REGEXkeywords. You can learn them by simply typing
lftp, and as soon as an lftp shell is opened, type
? and press Enter or
? lftp-command-you-want and press Enter. Example:
[root@host ~]# lftp lftp :~> ? !<shell-command> (commands) alias [<name> [<value>]] attach [PID] bookmark [SUBCMD] cache [SUBCMD] cat [-b] <files> cd <rdir> chmod [OPTS] mode file... close [-a] [re]cls [opts] [path/][pattern] debug [<level>|off] [-o <file>] du [options] <dirs> exit [<code>|bg] get [OPTS] <rfile> [-o <lfile>] glob [OPTS] <cmd> <args> help [<cmd>] history -w file|-r file|-c|-l [cnt] jobs [-v] [<job_no...>] kill all|<job_no> lcd <ldir> lftp [OPTS] <site> ln [-s] <file1> <file2> ls [<args>] mget [OPTS] <files> mirror [OPTS] [remote [local]] mkdir [-p] <dirs> module name [args] more <files> mput [OPTS] <files> mrm <files> mv <file1> <file2> [re]nlist [<args>] open [OPTS] <site> pget [OPTS] <rfile> [-o <lfile>] put [OPTS] <lfile> [-o <rfile>] pwd [-p] queue [OPTS] [<cmd>] quote <cmd> repeat [OPTS] [delay] [command] rm [-r] [-f] <files> rmdir [-f] <dirs> scache [<session_no>] set [OPT] [<var> [<val>]] site <site-cmd> source <file> torrent [-O <dir>] <file|URL>... user <user|URL> [<pass>] wait [<jobno>] zcat <files> zmore <files> lftp :~> ? mget Usage: mget [OPTS] <files> Gets selected files with expanded wildcards -c continue, resume transfer -d create directories the same as in file names and get the files into them instead of current directory -E delete remote files after successful transfer -a use ascii mode (binary is the default) -O <base> specifies base directory or URL where files should be placed
The knowledge related to know that
mget would be the right command inside
lftp came from reading manpages and searching for keywords like “bulk”, “multi” or “mass”, and knowing that the
ftp(1) command also have the
mget command so, probably
lftp would have an equivalent.