Is there ever a reason to use scp instead of rsync?

Question

Is there a reason to use scp instead of rsync? I can see no reason for using scp ever again, rsync does everything that scp does, with more safety (can preserve symlinks etc).

Answer 1

If you have to copy a large number of files, or have large files, rsync over ssh will be much faster than scp.

Answer 2

scp provides a cp like method to copy files from one machine to a remote machine over a secure SSH connection.

rsync allows you to syncronise remote folders.

They are different programs and both have their uses. scp is always secure, whereas rsync must travel over SSH to be secure.

Answer 3

The bottom line, try to use rsync all the time. The details follow.

Use scp if you want to strictly populate the destination.

Use rsync if you want to have the choice between strictly populating the destination or populating-and-deleting-at the destination. When you deploy a system the --delete option ensures a clean deployment.

Suppose there is a folder a/empty and no such file as a/empty/file

Suppose there is a folder b/empty and also a file as b/empty/file, in other words, contrary to the appearance, it is not empty.

Contrast the following:

scp -r a/* b

rsync --delete --recursive a/* b.

In the case of rsync, the folder of the same name will be emptied. Of course, for both commands, whatever is caught by the wildcard, *, will cloned anew at the destination.

In order to minimize human error caused by lack of familiarity, just use rsync all the time, omitting the --delete option when you want behaviour like that of scp. rsync looks complicated, so use a script to constrain functionality, hopefully severely.

Here's one.

#!/bin/bash

# Presently, this script is named deploy.sh.
#
# It uses rsync, secured, to do something like a push scp.  
# Unlike scp files will be deleted at the destination.
# 
# RECOMMENDATION: To minimize risk, always use this script instead of
# invoking rsync directly for push operations.  
# Pulling via rsync seems less risky so I do not have a rsync wrapper for pulling.

SCRIPTNAME=$(basename $0)
if [ $SCRIPTNAME != "deploy.sh" ]
then
  printf "Are you sure this script is well named?\n"
  exit 0
fi

usage() {
  printf "usage:\n"
  printf "deploy.sh sourceFolder /path/destinationFolder [recursive]\n"
  printf "The destination path must be absolute.\n"
  printf "The sourceFolder must have the same name as the destinationFolder.\n"
  printf "You need to define an EV like this DESTINATIONIP=255.255.255.255.\n"
}

syncMethod1() {
  rsync --delete $3 --compress --progress \
    --times --perms --owner --group \
    --rsh="ssh" \
    "$1"/ root@$DESTINATIONIP:"$2"     
  # note the trailing slash on the source
  # note to use --delete you must omit the * at the end of the source
}

syncMethod0() {
  BASENAMESOURCE=$(basename $1)
  BASENAMEDESTINATION=$(basename $2)
  if [ $BASENAMESOURCE = $BASENAMEDESTINATION ]
  then
    syncMethod1 $1 $2 $3
  else
    usage
    printf "\nThe two folders must have the same name.\n"
  fi
}

FIRST=$1
SECOND=$2
THIRD=$3

if [ ! -d "$FIRST" ]
then
  usage
  printf "\nThe source must be a folder.\n"
elif [ $# != 2 ] && [ $# != 3 ]
then
  usage
  printf "\nWrong number of arguments.\n"
elif [ -z $DESTINATIONIP ]
then
  usage
  printf "\nUndefined DESTINATIONIP.\n"
elif [ ${SECOND:0:1} != "/" ]
then
  usage
  printf "\nDestination path error.\n"
else
  if [ $# = 2 ]
  then
    RECURSIONOPTION="--dirs"     # shallow
    syncMethod0 $FIRST $SECOND $RECURSIONOPTION
  elif [ $# = 3 ]
  then
    if [ "$THIRD" = "recursive" ]
    then
      RECURSIONOPTION="--recursive"
      syncMethod0 $FIRST $SECOND $RECURSIONOPTION
    else
      usage
      printf "\nUnknown parameter.\n"
    fi
  fi
fi
exit 0

Answer 4

scp is simpler to use as it takes less arguments. I catch myselv using scp instead of rsync if I only transfer a single file. Propably I am just to lazy to define an alias to rsync... ;-)