| 1 | #! /bin/bash |
| 2 | |
| 3 | set -e |
| 4 | |
| 5 | # Defaults |
| 6 | prefix='/dev/shm/khatus' |
| 7 | host="$(hostname)" |
| 8 | sensor="$(basename $0)" |
| 9 | run_in='foreground' # foreground | background |
| 10 | run_as='poller' # poller | streamer |
| 11 | interval=1 # Only relevant if run_as poller, ignored otherwise. |
| 12 | |
| 13 | set_common_options() { |
| 14 | while : |
| 15 | do |
| 16 | case "$1" |
| 17 | in '') |
| 18 | break |
| 19 | ;; -d|--daemon) |
| 20 | run_in='background' |
| 21 | shift 1 |
| 22 | ;; -i|--interval) |
| 23 | case "$2" |
| 24 | in '') |
| 25 | printf "Option $1 requires and argument\n" >&2 |
| 26 | exit 1 |
| 27 | ;; *) |
| 28 | interval="$2" |
| 29 | shift 2 |
| 30 | esac |
| 31 | ;; *) |
| 32 | shift 1 |
| 33 | esac |
| 34 | done |
| 35 | } |
| 36 | |
| 37 | init_dirs() { |
| 38 | work_dir="${prefix}/${host}/${sensor}" |
| 39 | out_dir="${work_dir}/out" |
| 40 | err_file="${work_dir}/err" |
| 41 | pid_file="${work_dir}/pid" |
| 42 | |
| 43 | mkdir -p "$out_dir" |
| 44 | } |
| 45 | |
| 46 | streamer() { |
| 47 | sensor \ |
| 48 | | while read key val |
| 49 | do |
| 50 | printf "%s\n" "$val" > "${out_dir}/${key}" |
| 51 | done |
| 52 | >> "$err_file" |
| 53 | } |
| 54 | |
| 55 | poller() { |
| 56 | while : |
| 57 | do |
| 58 | streamer |
| 59 | sleep "$interval" |
| 60 | done |
| 61 | } |
| 62 | |
| 63 | pid_file_create_of_parent() { |
| 64 | printf "$$\n" > "$pid_file" |
| 65 | } |
| 66 | |
| 67 | pid_file_create_of_child() { |
| 68 | printf "$!\n" > "$pid_file" |
| 69 | } |
| 70 | |
| 71 | pid_file_test() { |
| 72 | if test -e "$pid_file" |
| 73 | then |
| 74 | printf "Error - $sensor already running (i.e. PID file exists at $pid_file)\n" 1>&2 |
| 75 | exit 1 |
| 76 | fi |
| 77 | } |
| 78 | |
| 79 | pid_file_remove() { |
| 80 | rm -f "$pid_file" |
| 81 | } |
| 82 | |
| 83 | run_in_foreground() { |
| 84 | # TODO: Why do INT and EXIT traps only work in combination? |
| 85 | trap true INT |
| 86 | trap exit TERM |
| 87 | trap pid_file_remove EXIT |
| 88 | $run_as |
| 89 | } |
| 90 | |
| 91 | run_in_background_2nd_fork() { |
| 92 | run_in_foreground & |
| 93 | pid_file_create_of_child |
| 94 | } |
| 95 | |
| 96 | run_in_background() { |
| 97 | run_in_background_2nd_fork & |
| 98 | } |
| 99 | |
| 100 | run() { |
| 101 | case "$run_as" |
| 102 | in 'poller' | 'streamer') |
| 103 | true |
| 104 | ;; *) |
| 105 | printf "Error - illegal value for \$run_as: $run_in\n" 1>&2 |
| 106 | exit 1 |
| 107 | esac |
| 108 | pid_file_test |
| 109 | case "$run_in" |
| 110 | in 'background') |
| 111 | run_in_background |
| 112 | ;; 'foreground') |
| 113 | pid_file_create_of_parent |
| 114 | run_in_foreground |
| 115 | ;; *) |
| 116 | printf "Error - illegal value for \$run_in: $run_in\n" 1>&2 |
| 117 | exit 1 |
| 118 | esac |
| 119 | } |
| 120 | |
| 121 | set_common_options $@ |
| 122 | init_dirs |