About how to use expr

naihe2010 · 10-31-2005, 12:51 AM

I use "expr" to do something,and it can't work.

Code:

$ expr 1+2
1+2
$ expr "1+2"
1+2
$ expr a=d
a=d
$ expr 10
10
$ expr abcde
abcde
$ expr abc +12
expr: syntax error
$ expr abc+12
abc+12

I think the first line is right,but it can't work,so I tried the others.

zhangmaike · 10-31-2005, 02:41 AM

You need spaces between the numbers and the operators.

Code:

$ expr 1 + 2
3

In bash, you don't need spaces if you use $(( ))

Code:

$ echo $((1+2))
3

naihe2010 · 10-31-2005, 06:28 AM

Very thank you.