关于ssh_copy_id脚本解析

[oldgirl@module ~]$ more /usr/bin/ssh-copy-id
#!/bin/sh

# Shell script to install your public key on a remote machine
# Takes the remote machine name as an argument.
# Obviously, the remote machine must accept password authentication,
# or one of the other keys in your ssh-agent, for this to work.

###########################################
##ssh-copy-id -i .ssh/id_dsa.pub oldgirl@192.168.127.128##
###########################################
ID_FILE="${HOME}/.ssh/id_rsa.pub"

if [ "-i" = "$1" ]; then #判断第一个参数是不是-i
shift #参数前移
# check if we have 2 parameters left, if so the first is the new ID file
###########################################
##ssh-copy-id .ssh/id_dsa.pub oldgirl@192.168.127.128##
###########################################
if [ -n "$2" ]; then #判断第二个参数是否非空
if expr "$1" : ".*\.pub" > /dev/null ; then #判断第一个参数是否匹配".pub"
ID_FILE="$1"
else
ID_FILE="$1.pub"
fi
shift # and this should leave $1 as the target name
fi
else
if [ x$SSH_AUTH_SOCK != x ] ; then
GET_ID="$GET_ID ssh-add -L"
fi
fi
###########################################
##ssh-copy-id oldgirl@192.168.127.128##
###########################################
if [ -z "`eval $GET_ID`" ] && [ -r "${ID_FILE}" ] ; then #把 “cat .ssh/id_dsa.pub” 内容赋值给GET_ID
GET_ID="cat ${ID_FILE}"
fi

if [ -z "`eval $GET_ID`" ]; then
echo "$0: ERROR: No identities found" >&2
exit 1
fi

if [ "$#" -lt 1 ] || [ "$1" = "-h" ] || [ "$1" = "--help" ]; then #错误提示
echo "Usage: $0 [-i [identity_file]] [user@]machine" >&2
exit 1
fi

{ eval "$GET_ID" ; }##解析命令“cat .ssh/id_dsa.pub”## | ssh $1 "umask 077; test -d ~/.ssh || mkdir ~/.ssh##创建目录## ; cat >> ~/.ssh/authorized_keys ##内容放到authorized_keys## && (test -x /sbin/r
estorecon && /sbin/restorecon ~/.ssh ~/.ssh/authorized_keys ##权限问题## >/dev/null 2>&1 || true)" || exit 1

cat <<EOF
Now try logging into the machine, with "ssh '$1'", and check in:

.ssh/authorized_keys

to make sure we haven't added extra keys that you weren't expecting.

EOF