说明awk中变量作用域之前,先看几个测试
测试1:fun1()没有参数,里面的变量x和BEGIN里的x是同一个变量
[email protected]:~$ cat test1.awk
BEGIN {
x = "Good"
fun1()
print "X in BEGIN is", x
}
function fun1() {
print "X in fun1 before reassign is", x
x = "Bad"
print "X in fun1 after reassign is", x
}
[email protected]:~$ awk -f test1.awk
X in fun1 before reassign is Good
X in fun1 after reassign is Bad
X in BEGIN is Bad
测试2:fun1()有参数,则里面的变量x仅在函数内部有效,和BEGIN里的x变量是两个不同的变量
[email protected]:~$ cat test2.awk
BEGIN {
x = "Good"
fun1(x)
print "X in BEGIN is", x
}
function fun1(x) {
print "X in fun1 before reassign is", x
x = "Bad"
print "X in fun1 after reassign is", x
}
[email protected]:~$ awk -f test2.awk
X in fun1 before reassign is Good
X in fun1 after reassign is Bad
X in BEGIN is Good
测试3:把测试2中的变量换为数组,参数换为数组名
[email protected]:~$ cat test3.awk
BEGIN {
A[1] = "Good"
fun1(A)
print "A[1] in BEGIN is", A[1]
}
function fun1(A) {
print "A[1] in fun1 before reassign is", A[1]
A[1] = "Bad"
print "A[1] in fun1 after reassign is", A[1]
}
[email protected]:~$ awk -f test3.awk
A[1] in fun1 before reassign is Good
A[1] in fun1 after reassign is Bad
A[1] in BEGIN is Bad
测试4:
[email protected]:~$ cat test4.awk
BEGIN {
fun1()
fun2()
}
function fun1() {
x = "Hello"
}
function fun2() {
print x ? x : "NULL"
}
[email protected]:~$ awk -f test4.awk
Hello
[email protected]:
测试5:
[email protected]:~$ cat test5.awk
BEGIN {
fun1("Good")
fun2()
}
function fun1(x) {
x = "Hello"
}
function fun2() {
print x ? x : "NULL"
}
[email protected]:~$ awk -f test5.awk
NULL
通过以上测试,可以看出,变量的作用域是从第一次出现开始,直到整个程序的结束为止。如果变量是在某个函数中出现,那么要看函数定义时的参数中是否有此变量,如果有,那么只在这个函数中有效;否则,从函数被调用开始有效,一直到整个程序结束。如果是数组名作为函数参数,是个例外,因为数组名是个地址。