Checking FTP connectivity to remote host

[talisker123gjs]

Hi
If I try to ftp an invalid IP address, I get no result (which is obvious) and the command seems to be hanging.

HOW DO I TRAP THIS KIND OF ERROR ?

For eg., I am using FTP in a "here" document within a shell script. If the remote system isn't available or if there is a network problem, how can my script trap such errors?

I am using the ksh on SunOS 5.6.

Thanks

 

[vgersh99]

'ping' first.
'ftp' next checking the return status of 'ftp' itself [${?}].

vlad
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[marsd]

Best probably to just use a more reliable language
than shell for this.
I don't understand why people continue to use here docs
for automating ftp when better tools are all over the
place including expect: http:/expect.nist.gov, tcl and
perl.

Brief tcl example:

#!/usr/bin/tclsh
package require ftp 2.3.1
#procedure to prompt user for input#
proc getin {msg} {
   puts -nonewline stdout $msg
   flush stdout
   return [gets stdin]
}

proc progressive {bytes} {
     puts -nonewline stdout "#"
     flush stdout
     return $bytes
}


   if {![llength $argv]} { error "Cannot call script without host(1) and username(2)"}
      set host [lindex $argv 0]
      set uname [lindex $argv 1]


    if {[set handle [ftp::Open $host $uname [getin "Please enter your password: "]  -progress progressive]] >= 0} {
       puts "Opened connection successfully to $host\n"
       after 2500 
       ftp::Close $handle
     } else {
          error "Unable to open connectiion to host: $host"
     }

 

[vgersh99]

1. tcl and expect are not generally available for some OS
distributions. Implementing a solutions with a 'gnerally
available' tools sometimes is a prerequisite.

2. not being fluent with perl is another reason.

3. not being fully aware of the 'gottachas' of the 'here-docs'
and knowing the ways around it is another reason.

4. you're as good as your 'tool-box' is. And then you have
'tek-tips'.

vlad
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[marsd]

You're right vlad..but if there is a chance
of saving yourself the pain of writing a
script that may fail due to any number of
reasons, AND doesn't really provide
good network error detection, almost any
other solution is preferable IMO.

 

[talisker123gjs]

marsd
I have worked on Applications such as CONNECT DIRECT and XFB.CFT for doing FTP stuff. These applications provide secure FTP and good error-trapping.
However, for certain reasons, I was asked to use a shell script and hence I wanted to know if there're any error trapping mechanisms in shell scripts. I didn't have much hope that the Korn shell would provide me with a solution, but I started this thread to determine if there is a korn shell solution that I'm unaware of. Anyway, thanks for your Tcl code and relevant information.

vgersh99
Even if the remote system is available, checking for an exit status of 0 (ksh) need not always indicate successful FTP. Also, I agree with your 4-point post.

 

[vgersh99]

the most common way of 'error trapping mechanisms' with here-doc with ftp is to redirect the stderr of of ftp and 'parse' the resulting error file for errors/success:

ftp -n -v > 2> /tmp/errFile.txt <<EOF
ftp commands here
....
EOF

parseErrFile '/tmp/errFile.txt'

vlad
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