[Unix] C Shell (csh) continue 用法等价: Resume execution of a loop

Overview

The continue command in C Shell (csh) is used within loops to skip the remaining commands in the current iteration and proceed to the next iteration of the loop. This is particularly useful when you want to bypass certain conditions without terminating the entire loop.

Usage

The basic syntax of the continue command is as follows:

continue [n]

Here, n is an optional argument that specifies how many levels of nested loops to continue. If n is not provided, it defaults to 1, meaning it will continue the innermost loop.

Common Options

• n: Specifies the number of nested loops to continue. If you have multiple nested loops, you can use this option to skip to the next iteration of a specific loop level.

Common Examples

Example 1: Basic usage in a loop

In this example, the loop iterates through numbers 1 to 5, but skips the number 3.

foreach i (1 2 3 4 5)
    if ($i == 3) then
        continue
    endif
    echo $i
end

Output:

1
2
4
5

Example 2: Continuing a nested loop

Here’s an example with nested loops where we skip the inner loop when j is 2.

foreach i (1 2)
    foreach j (1 2 3)
        if ($j == 2) then
            continue 2
        endif
        echo "$i $j"
    end
end

Output:

1 1
1 3
2 1
2 3

Example 3: Using continue with a condition

In this example, we only print even numbers from 1 to 10.

foreach i (1 2 3 4 5 6 7 8 9 10)
    if ($i % 2 != 0) then
        continue
    endif
    echo $i
end

Output:

2
4
6
8
10

Tips

• Use continue to make your loops cleaner by avoiding deeply nested if statements.
• Always ensure that the condition for continue is clearly defined to avoid skipping unintended iterations.
• When using nested loops, specify the correct level with n to avoid confusion about which loop is being continued.