linux - 如何在子shell中设置变量？

Question

我有一个脚本，它将在每台服务器上运行，并将某些文件复制到其中。脚本知道我在哪里运行以及我需要复制哪些文件。

脚本将从本地数据中心 local_dc 复制文件，但如果它已关闭或没有响应，那么它将从远程数据中心 remote_dc_1 复制相同的文件，如果它也已关闭, 然后它将从另一个远程数据中心 remote_dc_2 复制相同的文件，如下所示。

现在假设如果 local_dc 机器宕机，那么它将从 remote_dc_1 机器复制文件，所以我需要发送一封电子邮件说这台机器宕机了，所以从其他远程机器。如果 local_dc 机器出现故障，我不想发送多封电子邮件，所以我在最后发送电子邮件，这样我只收到一封电子邮件，而不是每个文件收到多封电子邮件。

下面是我的脚本-

do_Copy() {
  el=$1
  PRIMSEC=$2
  scp david@"$local_dc":"$dir3"/new_weekly_2014_"$el"_200003_5.data "$PRIMSEC"/. \
    || (a=1 && scp david@"$remote_dc_1":"$dir3"/new_weekly_2014_"$el"_200003_5.data "$PRIMSEC"/.) \
    || (b=2 && scp david@"$remote_dc_2":"$dir3"/new_weekly_2014_"$el"_200003_5.data "$PRIMSEC"/.) \
    || (c=3 && exit 1)
}

export -f do_Copy

parallel --retries 10 -j 10 do_Copy {} $PRIMARY ::: "${PRIMARY_PARTITION[@]}" &
parallel --retries 10 -j 10 do_Copy {} $SECONDARY ::: "${SECONDARY_PARTITION[@]}" &
wait

# problem is this doesn't work at all?
if [ $a -eq 1 ]
then
   echo "Local machine $local_dc was down, so copied from Primary Remote machine $remote_dc_1" | mailx -r "david@host.com" -s "$local_dc machine down" "david@host.com"
fi
if [ $b -eq 2 ]
then
   echo "Primary Remote machine $remote_dc_1 was down, so copied from Secondary Remote machine $remote_dc_2" | mailx -r "david@host.com" -s "$remote_dc_1 machine down" "david@host.com"
fi
if [ $c -eq 3 ]
then
   echo "All three machine's are down. Exiting out." | mailx -r "david@host.com" -s "All three machine's are down" "david@host.com"
fi

我在子 shell 中使用变量 a、b 和 c 做错了吗？

Answer 1

您无法使用 shell 或环境变量将此状态传回，但文件系统上的标志可以很好地完成这项工作。

#!/bin/bash
export status_dir=$(mktemp -t -d transfer.XXXXXX)
cleanup() { rm -rf "$status_dir"; }
trap cleanup 0 # automatically clean up on exit

do_Copy() {
  el=$1
  PRIMSEC=$2
  scp david@"$local_dc":"$dir3"/new_weekly_2014_"$el"_200003_5.data "$PRIMSEC"/. \
    || { touch "$status_dir/local_down" && scp david@"$remote_dc_1":"$dir3"/new_weekly_2014_"$el"_200003_5.data "$PRIMSEC"/.; } \
    || { touch "$status_dir/primary_down" && scp david@"$remote_dc_2":"$dir3"/new_weekly_2014_"$el"_200003_5.data "$PRIMSEC"/.; } \
    || { touch "$status_dir/secondary_down"; exit 1; }
}

...以及以后...

[[ -e "$status_dir/local_down" ]] && \
   mailx -r "david@host.com" -s "$local_dc machine down" "david@host.com" \
     <<<"Local machine $local_dc was down, so copied from Primary Remote machine $remote_dc_1"

[[ -e "$status_dir/primary_down" ]] && \
   mailx -r "david@host.com" -s "$remote_dc_1 machine down" "david@host.com" \
     <<<"Primary Remote machine $remote_dc_1 was down, so copied from Secondary Remote machine $remote_dc_2"

[[ -e "$status_dir/secondary_down" ]] && \
   mailx -r "david@host.com" -s "All three machine's are down" "david@host.com" \
     <<<"All three machines are down. Exiting out."