使用expr命令计算整数加法时遭遇non-integer argument错误的解决咨询

云上老周

2026-4-21

Hey there! Let's work through why your expr command is throwing that non-integer argument error—this is a super common gotcha with the expr tool, so I’ve got a few fixes to try:

Double-check variable assignment spacing
Make sure you didn’t add spaces around the = when setting your variables. For example, num1 = 20 is wrong (it tries to run a command called num1 with arguments = and 20), but num1=20 is correct. Your code looks like it’s doing this right, but it’s worth double-checking if you accidentally added spaces when typing.
Ensure spaces around the + operator in expr
The expr command is picky about whitespace around operators. If you wrote expr $num1+$num2 (no spaces around +), it’ll treat the whole string like a single non-integer argument. Your code uses expr $num1 + $num2 which is correct, but confirm there are actual spaces before and after the + in your terminal input—sometimes accidental typos happen here.
Verify your variables hold pure integers
Run echo $num1 and echo $num2 to make sure they output just 20 and 5 with no extra spaces, newlines, or other characters. If, for example, num1 got set to " 20" (with a leading space) somehow, expr will reject it as a non-integer.
Switch to Bash’s built-in arithmetic expansion (easier alternative)
If you want to avoid expr’s quirks entirely, Bash has its own way to do arithmetic that’s more forgiving. Just use this syntax instead:
```
num1=20
num2=5
echo $((num1 + num2))
```
This will output 25 without any of expr’s whitespace headaches.