个人整理的Linux Shell语法速查表（用C语言语法来作对比）

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: $1" shift done
逻辑/数值运算	if (d == 0) if (d != 0) if (d > 0) if (d < 0) if (d <= 0) if (d >= 0)	if [ "$D" -eq "0" ] ; then if [ "$D" -ne "0" ] ; then if [ "$D" -gt "0" ] ; then if [ "$D" -lt "0" ] ; then if [ "$D" -le "0" ] ; then 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); printf( “%d”, D); printf( “%d\n”,D);	read D echo –n $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 $COUNTER + 1` done
	while (1) { } break; continue;	while : do done break或break n，n表示跳出n级循环 continue
函数与过程的定义	void hello() { printf( “hello\n” ); } … //函数调用 hello();	hello() { Echo “hello” } 或者 function hello() { Echo “hello” } … #函数调用 hello
函数的参数和返回值	int ret = doIt(); if (ret == 0) { printf( “OK\n” ); }	doIt if [ “$?” –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