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shell中常用功能与C语言的对比

2014-09-04 15:23 447 查看
要实现的功能
C语言编程
Linux Shell脚本编程
程序/脚本的参数传递
int main(int argc, char** argv)
{

if (argv != 4) {

printf( “Usage: %s arg1 arg2 arg3”, argv[0] );

return 1;

}

printf(“arg1:%s\n”,argv[1]);

printf(“arg2:%s\n”,argv[2]);

printf(“arg3:%s\n”,argv[3]);

return 0;
}
#!/bin/sh

if [ $# -lt 3 ]; then
echo "Usage: `basename $0` arg1 arg2 arg3" >&2
exit 1
fi

echo "arg1: $1"
echo "arg2: $2"
echo "arg3: $3"
exit 0
int main(int argc, char** argv)
{
int i;

for (i=1; i<=argc;i++) {

printf(“arg:%s\n”,argv[i]);

}

return 0;
}
#!/bin/sh

while [ $# -ne 0 ]
do
echo "arg: $1"
shift
done
逻辑/数值运算
if (d == 0)
if [ "$D" -eq "0" ] ; then
if (d != 0)
if [ "$D" -ne "0" ] ; then
if (d > 0)
if [ "$D" -gt "0" ] ; then
if (d < 0)
if [ "$D" -lt "0" ] ; then
if (d <= 0)
if [ "$D" -le "0" ] ; then
if (d >= 0)
if [ "$D" -ge "0" ] ; then
字符串比较
if (strcmp(str,”abc”)==0) {
}
if [ "$STR" != "abc" ]; then
fi
输入和输出
scanf(“%d”,&D);
read D
printf( “%d”, D);
echo –n $D
printf( “%d”,D);
echo $D
printf( “Press any to continue...”);
char ch=getchar();
printf( “\nyou pressed: %c\n”, ch );
#!/bin/sh

getchar()
{
SAVEDTTY=`stty -g`
stty cbreak
dd if=/dev/tty bs=1 count=1 2> /dev/null
stty -cbreak
stty $SAVEDTTY
}

echo -n "Press any key to continue..."
CH=`getchar`
echo ""
echo "you pressed: $CH"
read D <&3
程序/脚本的控制流程
if (isOK) {
//1
} else if (isOK2) {
//2
} else {
//3
}
if [ isOK ]; then
#1
elif [ isOK2 ]; then
#2
else
#3
fi
switch (d)
{
case 1:

printf(“you select 1\n”);

break;
case 2:
case 3:

printf(“you select 2 or 3\n”);

break;
default:

printf(“error\n”);

break;
};
case $D in
1) echo "you select 1"
;;
2|3) echo "you select 2 or 3"
;;
*) echo "error"
;;
esac
for (int loop=1; loop<=5;loop++) {
printf( “%d”, loop);
}
for loop in 1 2 3 4 5
do
echo $loop
done
do {
sleep(5);
} while( !isRoot );
IS_ROOT=`who | grep root`
until [ "$IS_ROOT" ]
do
sleep 5
done
counter=0;
while( counter < 5 ) {

printf( “%d\n”, counter);

counter++;
}
COUNTER=0
while [ $COUNTER -lt 5 ]
do

echo $COUNTER
COUNTER=`expr $COUNTER + 1`
done
while (1) {
}
while :
do
done
break;
break或break n，n表示跳出n级循环
continue;
continue
函数与过程的定义
void hello()
{
printf( “hello\n” );
}
…
//函数调用
hello();
hello()
{
Echo “hello”
} 或者
function hello()
{
Echo “hello”
}
…
#函数调用
hello
函数的参数和返回值
int ret = doIt();
if (ret == 0) {
printf( “OK\n” );
}
doIt
if [ “$?” –eq 0 ] ; then

echo “OK”
fi
或者
RET = doIt
if [ “$RET” –eq “0” ] ; then

echo “OK”
fi
int sum(int a,int b)
{

return a+b;
}
int s = sum(1,2);
printf(“the sum is: %d\n”, s);
sum()
{
echo -n "`expr $1 + $2`"
}
S=`sum 1 2`
echo "the sum is: $S"
bool isOK() { return false; }
if (isOK) {
printf( “YES\n” );
} else {
printf( “NO\n” );
}
isOK()
{
return 1;
}
if isOK ; then
echo "YES"
else
echo "NO"
fi
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