读取字符串并转换为 INT (BASH)
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Read string and convert to INT (BASH)
提问by sjsam
i have a simple script in Bash wich read a number in a file and then compare it with a different threshholds. The output is this:
我在 Bash 中有一个简单的脚本，它读取文件中的一个数字，然后将它与不同的阈值进行比较。输出是这样的：
: integer expression expected
: integer expression expected
OK: 3
My code is this:
我的代码是这样的：
#!/bin/bash
wget=$(wget http://10.228.28.8/ -O /tmp/wget.txt 2>/dev/null)
output=$(cat /tmp/wget.txt | awk 'NR==6')
#output=7
echo $output
if [ $output -ge 11 ];then
echo "CRITICAL: $output"
exit 2
elif [ $output -ge 6 ] && [ $output -lt 11 ];then
echo "WARNING: $output"
exit 1
else
echo "OK: $output"
exit 0
fi
rm /tmp/wget.txt
I know what is the problem, i kown that im reading a string and i try to compare a int. But i dont know how can i do to read this file and convert the number to read in a int var..
我知道问题出在哪里，我知道我正在读取一个字符串，并尝试比较一个 int。但我不知道我该怎么做才能读取这个文件并将数字转换为读入 int var ..
Any ideas?
有任何想法吗？
Thanks.
谢谢。
回答by chepner
The problem occurs when $outputis the empty string; whether or not you quote the expansion (and you should), you'll get the integer expression required error. You need to handle the empty string explictly, with a default value of zero (or whatever default makes sense).
问题出现的时候$output是空字符串；无论您是否引用扩展（并且应该引用），您都会得到整数表达式所需的错误。您需要显式地处理空字符串，默认值为零（或任何有意义的默认值）。
wget=$(wget http://10.228.28.8/ -O /tmp/wget.txt 2>/dev/null)
output=$(awk 'NR==6' < /tmp/get.txt)
output=${output:-0}
if [ "$output" -ge 11 ];then
echo "CRITICAL: $output"
exit 2
elif [ "$output" -ge 6 ];then
echo "WARNING: $output"
exit 1
else
echo "OK: $output"
exit 0
fi
(If you reach the elif, you already know the value of $outputis less than 11; there's no need to check again.)
（如果到达elif，则已经知道 的值$output小于 11；无需再次检查。）
The problem also occurs, and is consistent with the error message, if outputends with a carriage return. You can remove that with
问题也出现了，和错误信息一致，如果output以回车结束。你可以用
output=${output%$'\r'}
回答by sjsam
There are a couple of suggestions from my side regarding your code.
我这边有一些关于您的代码的建议。
You could explicitly tell bash the outputis an integer
你可以明确地告诉 bash 这output是一个整数
declare -i output # See [1]
Change
改变
output=$(cat /tmp/wget.txt | awk 'NR==6') # See [2]
may be better written as
可能更好地写成
output=$(awk 'NR==6' /tmp/wget.txt )
Change
改变
if [ $output -ge 11 ]
to
到
if [ "0$output" -ge 11 ] # See [4]
or
或者
if (( output >= 11 )) # Better See [3]
References
参考
- Check bash [ declare ].
- Useless use of cat. Check [ this ]
Quoting [ this ]answer :
((...))enable you to omit the dollar signs on integer and array variables and include spaces around operators for readability. Also empty variable automatically defaults to 0 in such a statement.- The zero in the beginning of
"0$output"help you deal with empty$output
- 检查 bash [声明]。
- 用猫没用。检查[这个]
引用[this]答案：
((...))使您能够省略整数和数组变量上的美元符号，并在运算符周围包含空格以提高可读性。在这样的语句中，空变量也会自动默认为 0。- 零开头
"0$output"帮你处理空$output
InterestingUseless use of catis a phrase that has been resounding in SO for long. Check [ this ]
[ @chepner ]has dealt with the empty outputfiasco using [ bash parameter expansion ]in his [ answer ], worth having a look at.
有趣Useless use of cat是一个在 SO 中响彻很久的短语。检查[this]
[@chepner]在他的[answer] 中output使用[bash 参数扩展]处理了空惨败，值得一看。
回答by Manuel Alcocer
In BASH, It is a good idea to use double brackets for strings:
在 BASH 中，对字符串使用双括号是个好主意：
if [[ testing strings ]]; then
<whatever>
else
<whatever>
fi
Or double parenthesis for integers:
或整数的双括号：
if (( testing ints )); then
<whatever>
else
<whatever>
fi
For example try this:
例如试试这个：
var1="foo bar"
if [ $var1 == 'foo bar' ]; then
echo "ok"
fi
Result:
结果：
$ bash: [: too many arguments
Now, this:
现在，这个：
var2="foo bar"
if [[ $a == "foo bar" ]]; then
echo "ok"
fi
Result:
结果：
ok
For that, your code in BASH:
为此，您在 BASH 中的代码：
if [[ $output -ge 11 ]]; then
echo "CRITICAL: $output"
exit 2
elif [[ $output -ge 6 ]]; then
echo "WARNING: $output"
exit 1
else
echo "OK: $output"
exit 0
fi
回答by Manuel Alcocer
A simplified script:
一个简化的脚本：
#!/bin/bash
wget=$(wget http://10.228.28.8/ -O /tmp/wget.txt 2>/dev/null)
output=$(awk 'NR==6' </tmp/wget.txt )
output="$(( 10#${output/[^0-9]} + 0 ))"
(( output >= 11 )) && { echo "CRITICAL: $output"; exit 2; }
(( output >= 6 )) && { echo "WARNING: $output"; exit 1; }
echo "OK: $output"
The key line to cleanup any input is:
清理任何输入的关键行是：
output="$(( 10#${output/[^0-9]} + 0 ))"
${output/[^0-9]}Will leave only digits from 0 to 9.
${output/[^0-9]}将只留下 0 到 9 的数字。
10#${output/[^0-9]}Will convert outputto a base 10 number.
10#${output/[^0-9]}将转换output为基数为 10 的数字。
That will correctly convert numbers like 0019
这将正确转换数字，如 0019
"$(( 10#${output/[^0-9]} + 0 ))"Will produce a zero for a missing value.
"$(( 10#${output/[^0-9]} + 0 ))"将为缺失值生成零。
Then the resulting number stored in output will be compared to limits and the corresponding output will be printed.
然后存储在输出中的结果数字将与限制进行比较，并打印相应的输出。
