从每个文件中读取第一行并将它们与参考号进行比较

I have three input files. I will read the first line of each the input file and I will compare them to a reference number. All values (a1,a2 and a3) I read from different input files should smaller than my "absolute reference value (aref)". My script gives the error for the reference value: line ..: -2.13: No such file or directory. How can I fix my code? And my if condition is correct?

我有三个输入文件。我将读取每个输入文件的第一行,我将它们与参考编号进行比较。从不同输入文件读取的所有值(a1,a2和a3)应小于我的“绝对参考值(aref)”。我的脚本给出了参考值的错误:line ..:-2.13:没有这样的文件或目录。我该如何修复我的代码?我的条件是否正确?

#!/bin/bash -f

a1=$(head -n 1 input1.xvg)
a2=$(head -n 1 input2.xvg)
a3=$(head -n 1 input3.xvg)

aref=-2.13

if [a1 < $aref && a2 < $aref && a3 < $aref] ; then

    echo "It's good"

else 

   echo "It isn't good"

fi

2 个解决方案

#1

As well as your syntax errors (you need spaces after [ and before ] in a test and you're missing some $ from your variable names), it looks like you're trying to compare floating point numbers, which is not supported by bash. One option would be to use bc, inside an arithmetic context instead:

除了你的语法错误(在测试中[和之前]需要空格并且你从变量名中遗漏了一些$),看起来你正在尝试比较bash不支持的浮点数。。一种选择是在算术上下文中使用bc:

if (( $(bc <<<"$a1 < $aref && $a2 > $aref && $a3 > $aref") )); then
    echo "It's good"
else
    echo "It isn't good"
fi

The output of the command substitution $( ... ), is 1 or 0, depending on whether the conditions are true or false. The arithmetic context (( ... )) returns success if the output is returns 1 and failure if it returns 0.

命令替换$(...)的输出为1或0,具体取决于条件是true还是false。如果输出返回1,则算术上下文((...))返回成功,如果返回0则返回失败。

If you would like to work with the absolute values of your variables, one way to do so would be to use ${a1#-}, ${aref#-}, etc. which removes the leading - from each variable.

如果你想使用变量的绝对值,一种方法是使用$ {a1# - },$ {aref# - }等来删除每个变量的前导值。

#2

Use [[ instead of [ in your if statement. Because you're using [ the shell thinks you are passing a file, not comparing to values.

使用[[而不是[在你的if语句中]。因为您正在使用[shell认为您正在传递文件,而不是与值进行比较。

Try to write your if like this

尝试写这样的if

if [[ $a1 < $aref && $a2 > $aref && $a3 > $aref ]] ; then

To use the absolute value of aref use this:

要使用aref的绝对值,请使用:

let "aref=$aref<0?-$aref:$aref"

#1

if (( $(bc <<<"$a1 < $aref && $a2 > $aref && $a3 > $aref") )); then
    echo "It's good"
else
    echo "It isn't good"
fi