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|
#!/bin/bash
#
# export_JSON <variables>
#
# Synopsis:
#
# $ (
# source export-json.bash
# export_JSON SSH_TTY \
# SSH_CONNECTION \
# SSH_CLIENT \
# SSH_AUTH_SOCK
# )
# {
# "SSH_TTY": "/dev/pts/0",
# "SSH_CONNECTION": "192.0.2.140 41564 198.51.100.25 22",
# "SSH_CLIENT": "192.0.2.140 41564 22",
# "SSH_AUTH_SOCK": "/tmp/ssh-XXXXcePKJl/agent.36326"
# }
#
# This bash function exports shell variables as
# JSON ("javascript object notation") strings.
#
# The string is printed to stdout.
#
# JSON is a format that represents data as
# Javascript source code so modern programmers
# can read it unlike bash source code.
#
# Variable names are given to the function as its
# argument list:
#
# $ (source export-json.bash; export_JSON PATH)
#
# The output is a single JSON object containing
# key-value mappings between JSON strings:
#
# {
# "PATH": "/usr/local/sbin:[...]"
# }
#
# It uses the external tool "jq" to parse string
# values placed in jq's argument list by bash and
# then encode them as JSON string values. This
# is no accidental dependency. The jq program is
# the foundation of the trustworthiness of this
# code. If we were encoding JSON strings in bash
# we would have to be a lot more careful.
arg1_to_env0()
{
case "$1" in
*[^a-zA-Z0-9_=]* )
echo "Error: invalid variable: '$1'" >&2
return 10
;;
[a-zA-Z_]* )
set -- "${1#*=}" "${1%%=*}"
;;
* )
echo "Error: invalid variable: '$1'" >&2
return 20
;;
esac
if [ -v "$2" ]
then
printf '%s=%s\0' "$1" "${!2}"
else
echo "Warning: ignoring unset variable: '$2'" >&2
fi
}
vars_to_env0()
{
while [ $# -gt 0 ]
do
arg1_to_env0 "$1" || return
shift
done
}
env0_to_JSON()
{
set --
while read -d ''
do
set -- "$@" --arg "${REPLY%%=*}" "${REPLY#*=}"
done
jq -n -r '$ARGS.named' "$@"
}
export_JSON_simple()
{
(
set -o pipefail
vars_to_env0 "$@" | env0_to_JSON
)
}
safe_stdout()
{
set -- "$(mktemp)" "$@"
if (shift; "$@") > "$1"
then
r=0
cat < "$1"
else
r=$?
fi
rm "$1"
return $r
}
export_JSON()
{
safe_stdout export_JSON_simple "$@"
}
try()
{
"$@"
printf '(Exit %s) <- [%s]\n' "$?" "${*@Q}" >&2
}
runtest()
{
set -- SSH_CLIENT SSH_TTY SSH_AUTH_SOCK SSH_CONNECTION
try export_JSON "$@"
unset unsetvar
try export_JSON SSH_TTY unsetvar
try export_JSON unsetvar SSH_TTY
try export_JSON
try export_JSON ''
try export_JSON '' SSH_TTY
}
|
