Linux 如何在 UNIX 中将字符串转换为整数
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How to convert string to integer in UNIX
提问by qwarentine
I have d1="11"and d2="07". I want to convert d1and d2to integers and perform d1-d2. How do I do this in UNIX?
我有d1="11"和d2="07"。我想将d1和转换d2为整数并执行d1-d2. 我如何在 UNIX 中执行此操作？
d1 - d2currently returns "11-07"as result for me.
d1 - d2目前"11-07"为我返回结果。
采纳答案by William Pursell
The standard solution:
标准解决方案：
expr $d1 - $d2
You can also do:
你也可以这样做：
echo $(( d1 - d2 ))
but beware that this will treat 07as an octal number! (so 07is the same as 7, but 010is different than 10).
但请注意，这将被07视为八进制数！（so07与 相同7，但010不同于10）。
回答by qwarentine
Use this:
用这个：
#include <stdlib.h>
#include <string.h>
int main()
{
const char *d1 = "11";
int d1int = atoi(d1);
printf("d1 = %d\n", d1);
return 0;
}
etc.
等等。
回答by Levon
Any of these will work from the shell command line. bcis probably your most straight forward solution though.
其中任何一个都可以在 shell 命令行中工作。bc不过，这可能是您最直接的解决方案。
Using bc:
使用bc：
$ echo "$d1 - $d2" | bc
Using awk:
使用awk：
$ echo $d1 $d2 | awk '{print - }'
Using perl:
使用perl：
$ perl -E "say $d1 - $d2"
Using Python:
使用Python：
$ python -c "print $d1 - $d2"
all return
全部返回
4
回答by mykeaka
let d=d1-d2;echo $d;
This should help.
这应该有帮助。
回答by Bruno Bronosky
An answer that is not limited to the OP's case
不限于OP案例的答案
The title of the question leads people here, so I decided to answer that question for everyone else since the OP's described case was so limited.
问题的标题将人们引到这里，因此我决定为其他所有人回答这个问题，因为 OP 描述的案例非常有限。
TL;DR
TL; 博士
I finally settled on writing a function.
我终于决定写一个函数。
- If you want
0in case of non-int:
- 如果你想
0在非整数的情况下：
int(){ printf '%d' ${1:-} 2>/dev/null || :; }
- If you want [empty_string]in case of non-int:
- 如果你想要[empty_string]在非整数的情况下：
int(){ expr 0 + ${1:-} 2>/dev/null||:; }
- If you want find the first int or [empty_string]:
- 如果你想找到第一个 int 或[empty_string]：
int(){ expr ${1:-} : '[^0-9]*\([0-9]*\)' 2>/dev/null||:; }
- If you want find the first int or 0:
- 如果你想找到第一个 int 或 0：
# This is a combination of numbers 1 and 2
int(){ expr ${1:-} : '[^0-9]*\([0-9]*\)' 2>/dev/null||:; }
If you want to get a non-zero status code on non-int, remove the ||:(aka or true) but leave the ;
如果您想在非整数上获得非零状态代码，请删除||:（又名或true）但保留;
Tests
测试
# Wrapped in parens to call a subprocess and not `set` options in the main bash process
# In other words, you can literally copy-paste this code block into your shell to test
( set -eu;
tests=( 4 "5" "6foo" "bar7" "foo8.9bar" "baz" " " "" )
test(){ echo; type int; for test in "${tests[@]}"; do echo "got '$(int $test)' from '$test'"; done; echo "got '$(int)' with no argument"; }
int(){ printf '%d' ${1:-} 2>/dev/null||:; };
test
int(){ expr 0 + ${1:-} 2>/dev/null||:; }
test
int(){ expr ${1:-} : '[^0-9]*\([0-9]*\)' 2>/dev/null||:; }
test
int(){ printf '%d' $(expr ${1:-} : '[^0-9]*\([0-9]*\)' 2>/dev/null)||:; }
test
# unexpected inconsistent results from `bc`
int(){ bc<<<"${1:-}" 2>/dev/null||:; }
test
)
Test output
测试输出
int is a function
int ()
{
printf '%d' ${1:-} 2> /dev/null || :
}
got '4' from '4'
got '5' from '5'
got '0' from '6foo'
got '0' from 'bar7'
got '0' from 'foo8.9bar'
got '0' from 'baz'
got '0' from ' '
got '0' from ''
got '0' with no argument
int is a function
int ()
{
expr 0 + ${1:-} 2> /dev/null || :
}
got '4' from '4'
got '5' from '5'
got '' from '6foo'
got '' from 'bar7'
got '' from 'foo8.9bar'
got '' from 'baz'
got '' from ' '
got '' from ''
got '' with no argument
int is a function
int ()
{
expr ${1:-} : '[^0-9]*\([0-9]*\)' 2> /dev/null || :
}
got '4' from '4'
got '5' from '5'
got '6' from '6foo'
got '7' from 'bar7'
got '8' from 'foo8.9bar'
got '' from 'baz'
got '' from ' '
got '' from ''
got '' with no argument
int is a function
int ()
{
printf '%d' $(expr ${1:-} : '[^0-9]*\([0-9]*\)' 2>/dev/null) || :
}
got '4' from '4'
got '5' from '5'
got '6' from '6foo'
got '7' from 'bar7'
got '8' from 'foo8.9bar'
got '0' from 'baz'
got '0' from ' '
got '0' from ''
got '0' with no argument
int is a function
int ()
{
bc <<< "${1:-}" 2> /dev/null || :
}
got '4' from '4'
got '5' from '5'
got '' from '6foo'
got '0' from 'bar7'
got '' from 'foo8.9bar'
got '0' from 'baz'
got '' from ' '
got '' from ''
got '' with no argument
Note
笔记
I got sent down this rabbit hole because the accepted answeris not compatible with set -o nounset(aka set -u)
我被送进了这个兔子洞，因为接受的答案与set -o nounset（又名set -u）不兼容
# This works
$ ( number="3"; string="foo"; echo $((number)) $((string)); )
3 0
# This doesn't
$ ( set -u; number="3"; string="foo"; echo $((number)) $((string)); )
-bash: foo: unbound variable
