How to convert string to integer in UNIX

问题

I have d1="11" and d2="07". I want to convert d1 and d2 to integers and perform d1-d2. How do I do this in UNIX?

d1 - d2 currently returns "11-07" as result for me.

回答1:

The standard solution:

 expr $d1 - $d2

You can also do:

echo $(( d1 - d2 ))

but beware that this will treat 07 as an octal number! (so 07 is the same as 7, but 010 is different than 10).

回答2:

Any of these will work from the shell command line. bc is probably your most straight forward solution though.

Using bc:

$ echo "$d1 - $d2" | bc

Using awk:

$ echo $d1 $d2 | awk '{print $1 - $2}'

Using perl:

$ perl -E "say $d1 - $d2"

Using Python:

$ python -c "print $d1 - $d2"

all return

4

回答3:

let d=d1-d2;echo $d;

This should help.

回答4:

Use this:

#include <stdlib.h>
#include <string.h>

int main()
{
    const char *d1 = "11";
    int d1int = atoi(d1);
    printf("d1 = %d\n", d1);
    return 0;
}

etc.

来源：https://stackoverflow.com/questions/11268437/how-to-convert-string-to-integer-in-unix