如何在bash for循环中执行psql命令 [英] How to execute a psql command within a bash for loop

问题描述

我想在bash脚本中执行psql语句并将结果输出到文件.我下面的代码可以按需工作:

I want to execute a psql statement within a bash script and output the results to a file. The code I have below works as desired:

#!/bin/bash

query="select * from mytable;"

psql <<EOF > output.txt
\timing
$query
EOF

我想运行该psql命令块5次，并将结果附加到output.txt.如果我再将其复制并粘贴4次，则效果很好，但是当我尝试将其放入for循环中时，会出现错误.有什么办法吗?

I want to run that psql command block 5 times and have the results appended to output.txt. It works fine if I just copy and paste it an additional 4 times, but when I try to put it inside of a for-loop, I get errors. Is there any way to do this?

这是我累的循环:

#!/bin/bash

query="select * from mytable;"

for (( i=0; i<5; i++ ))
do
   psql <<EOF > output.txt
   \timing
   $query
   EOF
done

如果我将最后一个EOF一直移到最左边，它只会执行一次，就好像循环不在那儿一样.

If I move the final EOF all the way over to the left, it only executes once, as if the loop wasn't there.

推荐答案

每次在循环内使用>覆盖文件.您需要在内部使用>>或在循环外部使用>:

You are overwriting the file each time with > inside the loop. You need >> inside or have > outside the loop:

#!/bin/bash

query="select * from mytable;"
for (( i=0; i<5; i++ ))
do
   psql <<EOF
   \timing
   $query
EOF
done > output.txt

在循环内将>放入done的效率要比>>高一点.

Putting > after done is a little more efficient than >> inside the loop.

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