[Buildroot] [PATCHv3 6/7] support/download/scp: implement source-check

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, All,

On 2019-02-09 21:23 +0100, Thomas De Schampheleire spake thusly:
> From: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
> 
> Signed-off-by: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
> ---
>  support/download/scp | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> v3: no changes
> 
> diff --git a/support/download/scp b/support/download/scp
> index 80cf495c4e..d81952956c 100755
> --- a/support/download/scp
> +++ b/support/download/scp
> @@ -7,17 +7,20 @@ set -e
>  #
>  # Options:
>  #   -q          Be quiet.
> +#   -C          Only check that the file exists remotely.
>  #   -o FILE     Copy to local file FILE.
>  #   -f FILE     Copy from remote file FILE.
>  #   -u URI      Download file at URI.
>  #
>  # Environment:
>  #   SCP       : the scp command to call
> +#   SSH       : the ssh command to use for checkonly
>  
>  verbose=
>  while getopts "${BR_BACKEND_DL_GETOPTS}" OPT; do
>      case "${OPT}" in
>      q)  verbose=-q;;
> +    C)  checkonly=1;;
>      o)  output="${OPTARG}";;
>      f)  filename="${OPTARG}";;
>      u)  uri="${OPTARG}";;
> @@ -33,8 +36,19 @@ shift $((OPTIND-1)) # Get rid of our options
>  _scp() {
>      eval ${SCP} "${@}"
>  }
> +_ssh() {
> +    eval ${SSH} "${@}"
> +}
>  
>  # Remove any scheme prefix
>  uri="${uri##scp://}"
>  
> +if [ -n "${checkonly}" ]; then
> +    # uri now looks like:  foo.example.org:some/directory
> +    domain="${uri%%:*}"
> +    path="${uri#*:}/${filename}"
> +    _ssh ${verbose} "${@}" "'${domain}'" ls "'${path}'" > /dev/null

I was going to reply to the previous thread, but you were too fast to
respin, so here's my proposal to avoid ls:

    /usr/bin/env [ -f "'${path}'" ]

It is almost impossible to have a system that lacks 'env' or that have
it in another location, as POSIX mandates env to exist, and IIRC, it
even mandates it to be /usr/bin/env (of is it FHS? at least, scripts in
Buildroot use "#!/usr/bin/env bash").

You may have to carefully quote the [ and ], to avoid the eval from
doing a nasty, weel, evaluation...

Regards,
Yann E. MORIN.

> +    exit ${?}
> +fi
> +
>  _scp ${verbose} "${@}" "'${uri}/${filename}'" "'${output}'"
> -- 
> 2.19.2
> 

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