我如何使用： cat << EOF

Question

我有点困惑，不确定如何将 cat << EOF 样式添加到我的脚本中。真的很感激一点反馈和帮助。

这是我的脚本

!/bin/sh
#This is a disk mailer script for hdfs    
DU_RESULTS_HOME=$(sudo -u hdfs hadoop fs -du -s /user/* | sort -r -k 1 -g | awk '{ suffix="KMGT"; for(i=0; $1>1024 && i < length(suffix); i++) $1/=1024; print int($1) substr(suffix, i, 1), $3; }'| head -n 22 |awk '{ print $1"\t\t\t" $2 }')

DF_RESULTS_HOME=$(sudo -u hdfs hadoop fs -df -h /user)
HOSTNAME=$(hostname -s)

MESSAGE_SUBJECT="Disk usage"
MESSAGE_SENDER="xyz"
MESSAGE_EMAIL="abc"

DU_RESULTS_HEADER_USER="Dir size             User"

MESSAGE_BODY="Team:

High level Disk Usage Report for: /user

Please take a moment to clean out any old data, and write temp files to an appropriate filesystem, such as /tmp.

Thanks

if [[ --debug == "$1" ]]; then
    echo debug on 
    printf '%s\n\n\n\n%s\n\n%s\n%s\n\n\n\n\n%s\n%s\n%s' "$MESSAGE_BODY" "$DF_RESULTS_HOME" "$DU_RESULTS_HEADER_USER" "$DU_RESULTS_HOME"
else                 
    echo debug off

    printf '%s\n\n\n\n%s\n\n%s\n%s\n\n\n\n\n%s\n%s\n%s' "$MESSAGE_BODY" "$DF_RESULTS_HOME" "$DU_RESULTS_HEADER_USER" "$DU_RESULTS_HOME" | /bin/mail -s "$MESSAGE_SUBJECT" -r "$MESSAGE_SENDER" "$MESSAGE_EMAIL"                        
fi

Answer 1

这<<是heredoc。任何跟在<<the 后面的东西都作为heredoc 的定界符

cat <<EOF
This is first line
So, this is 2nd
Again, another line
EOF

Enter

因此，如果您想将三行存储到变量中，请执行以下操作：

从命令行

$ var="$(cat <<EOF
> Bingo
> Gotcha
> Enough
> EOF
> )"

Enter

$ echo "$var" #double quotes are important
Bingo
Gotcha
Enough

从脚本内部

#!/bin/bash
var="$(cat <<EOF
Bingo
Gotcha
Enough
EOF
)"
echo "$var"