有没有一种在Linux中存储查询公式的方法？

Question

Linux can store functions, which can easily be called using the function system. If I wish to write several if statements however that should use the same reasoning, can this be done? For example:

if [ x == 1 ]
then
  ...
fi

If I need to use the x == 1 for umpteen formulas and vary all, can a block formula hold the equation so that I only need to make one modification instead of needing to modify all of them please?

Answer 1

You can just wrap your logic in a function and use the function as the condition in the if :

my_check() {
    [ "$x" -eq 1 ]
}

if my_check
then
    echo yes
else
    echo no
fi

This is taking advantage that the exit status of a shell function is the exit status of the last executed command. So if "$x" equals one the return status of my_check will be 0 (ie. success) and then you will enter the main branch. Otherwise exit status will be 1 (ie. failure) and then you will enter the alternate branch.

You could have multiple functions, one for each condition:

check_a() {
    [ "$x" -eq 1 ]
}

check_b() {
    [ "$x" -eq 2 ]
}

check_c() {
    [ "$y" -eq 1 ]
}

if check_a && check_c
then
    echo "a and c are true"
elif check_b && check_c
then
    ...
elif check_c
then
    ...
else
    ...
fi