一个子shell执行通话过程中的一个变量举行字符串麻烦转义引号 [英] Trouble escaping quotes in a variable held string during a Sub-shell execution call

问题描述

我想从一个bash脚本中写入数据库调用和我有一个子壳剥我的报价远的问题。

I'm trying to write a database call from within a bash script and I'm having problems with a sub-shell stripping my quotes away.

这是我在做什么骨头。

#---------------------------------------------    
#! /bin/bash    
export COMMAND='psql ${DB_NAME} -F , -t --no-align -c "${SQL}"  -o ${EXPORT_FILE} 2>&1'    
PSQL_RETURN=`${COMMAND}`    
#---------------------------------------------

如果我用一个回响，打印出$ {COMMAND}变量输出看起来不错：

If I use an 'echo' to print out the ${COMMAND} variable the output looks fine:

echo ${COMMAND}

屏幕输出： -

#---------------    
psql drupal7 -F , -t --no-align -c "SELECT DISTINCT hostname FROM accesslog;" -o /DRUPAL/INTERFACES/EXPORTS/ip_list.dat 2>&1    
#---------------

另外，如果我剪切并粘贴此屏幕输出它执行就好了。

Also if I cut and paste this screen output it executes just fine.

然而，当我尝试作为一个子shell调用中的变量要执行的命令，它给出了一个错误信息。
该错误是由psql客户端可以到报价已经从周围$ {} SQL字符串，删除的效果。
该错误表明在psql试图间preT中的SQL字符串作为参数的条件。

However, when I try to execute the command as a variable within a sub-shell call, it gives an error message. The error is from the psql client to the effect that the quotes have been removed from around the ${SQL} string. The error suggests psql is trying to interpret the terms in the sql string as parameters.

如此看来字符串和引号组成正确，但周围的$ {} SQL变量/字符串引号正在从主脚本执行通话过程中由子shell PTED间$ P $。

So it seems the string and quotes are composed correctly but the quotes around the ${SQL} variable/string are being interpreted by the sub-shell during the execution call from the main script.

我试着用各种方法逃离他们： \\，\\\\，\\\\\\，，\\''，\\'\\'，.. ......
正如你可以从我'试试'的做法看，我不是专家，它的驾驶我疯了。

I've tried to escape them using various methods: \", \\", \\\", "", \"" '"', \'"\', ... ... As you can see from my 'try it all' approach I am no expert and it's driving me mad.

任何帮助将大大AP preciated。

Any help would be greatly appreciated.

Charlie101

Charlie101

推荐答案

相反字符串中的无功储存指令更好地在这里使用BASH数组：

Instead of storing command in a string var better to use BASH array here:

cmd=(psql ${DB_NAME} -F , -t --no-align -c "${SQL}" -o "${EXPORT_FILE}")
PSQL_RETURN=$( "${cmd[@]}" 2>&1 )

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