int main()
 
{
 
int a = 42;
 
printf(“%d\n”, a);
 
}

#include <stdio.h>
 
void f(void)
 
{
 
static int a = 3;
 
static int b;
 
int c;
 
++a; ++b; ++c;
 
printf("a=%d\n", a);
 
printf("b=%d\n", b);
 
printf("c=%d\n", c);
 
}
 
int main(void)
 
{
 
f();
 
f();
 
f();
 
}

#include <stdio.h>
 
void foo(void)
 
{
 
int a;
 
printf("%d\n", a);
 
}
 
void bar(void)
 
{
 
int a = 42;
 
}
 
int main(void)
 
{
 
bar();
 
foo();
 
}

#include <stdio.h>
 
int b(void) { printf(“3”); return 3; }
 
int c(void) { printf(“4”); return 4; }
 
int main(void)
 
{
 
int a = b() + c();
 
printf(“%d\n”, a);
 
}

int a=41; a++; printf(“%d\n”, a);
 
int a=41; a++ & printf(“%d\n”, a);
 
int a=41; a++ && printf(“%d\n”, a);
 
int a=41; if (a++ < 42) printf(“%d\n”, a);
 
int a=41; a = a++; printf(“%d\n”, a);

struct X { int a; char b; int c; };
 
printf("%d,", sizeof(struct X));
 
struct Y { int a; char b; int c; char d};
 
printf("%d\n", sizeof(struct Y));

#include <stdio.h>
 
int main(void)
 
{
 
int a;
 
printf("%d\n", a);
 
}

#include <stdio.h>
 
int main(void)
 
{
 
int a[5];
 
printf("%x\n", a);
 
printf("%x\n", a+1);
 
printf("%x\n", &amp;a);
 
printf("%x\n", &amp;a+1);
 
}

++++ include/linux/kernel.h
159: #define min_t(type,x,y) \
160: ({ type __x = (x); type __y = (y); __x < __y ? __x: __y; })
++++ net/ipv4/tcp_output.c
654: int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk));

#define min(x,y) ((x) < (y) ? (x) : (y))

++++ include/linux/kernel.h
141: #define min(x,y) ({ \
142: const typeof(x) _x = (x); \
143: const typeof(y) _y = (y); \
144: (void) (&_x == &_y); \
145: _x < _y ? _x : _y; })

++++ include/linux/minix_fs.h
85: struct minix_dir_entry {
86: __u16 inode;
87: char name[0];
88: };

++++ include/linux/kernel.h
110: #define pr_debug(fmt,arg...) \
111: printk(KERN_DEBUG fmt,##arg)

pr_debug("%s:%d",filename,line)

printk("<7>"  "%s:%d", filename, line)

pr_debug("success!\n")

printk("<7>"  "success!\n")

+++++ arch/i386/kernel/irq.c
1079: static unsigned long irq_affinity [NR_IRQS] = { [0 ... NR_IRQS-1] = ~0UL };

++++ fs/ext2/file.c
41: struct file_operations ext2_file_operations = {
42: llseek: generic_file_llseek,
43: read: generic_file_read,
44: write: generic_file_write,
45: ioctl: ext2_ioctl,
46: mmap: generic_file_mmap,
47: open: generic_file_open,
48: release: ext2_release_file,
49: fsync: ext2_sync_file,
50 };

++++ arch/i386/kernel/irq.c
1062: case '0' ... '9': c -= '0'; break;
1063: case 'a' ... 'f': c -= 'a'-10; break;
1064: case 'A' ... 'F': c -= 'A'-10; break;
case '0' ... '9':

case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':

__attribute__ (( ATTRIBUTE ))

++++ include/linux/kernel.h
47: # define ATTRIB_NORET __attribute__((noreturn)) ....
61: asmlinkage NORET_TYPE void do_exit(long error_code)

++++ include/linux/kernel.h?
89: asmlinkage int printk(const char * fmt, ...)
90: __attribute__ ((format (printf, 1, 2)));

++++ fs/ext2/super.c
98: void ext2_update_dynamic_rev(struct super_block *sb)
99: {
100: struct ext2_super_block *es = EXT2_SB(sb)->s_es;
101:
102: if (le32_to_cpu(es->s_rev_level) > EXT2_GOOD_OLD_REV)
103: return;
104:
105: ext2_warning(sb, __FUNCTION__,
106: "updating to rev %d because of new feature flag, "
107: "running e2fsck is recommended",
108: EXT2_DYNAMIC_REV);

++++ kernel/sched.c
437: printk(KERN_ERR "schedule_timeout: wrong timeout "
438: "value %lx from %p\n", timeout,
439: __builtin_return_address(0));

++++ include/asm-i386/bitops.h
249: #define test_bit(nr,addr) \
250: (__builtin_constant_p(nr) ? \
251: constant_test_bit((nr),(addr)) : \
252: variable_test_bit((nr),(addr)))

++++ include/linux/compiler.h
13: #define likely(x) __builtin_expect((x),1)
14: #define unlikely(x) __builtin_expect((x),0)
++++ kernel/sched.c
564: if (unlikely(in_interrupt())) {
565: printk("Scheduling in interrupt\n");
566: BUG();
567: }

$ which bash

#!/bin/bash
# declare STRING variable
STRING="Hello World"
#print variable on a screen
echo $STRING

$ chmod +x hello_world.sh

./hello_world.sh

#!/bin/bash
tar -czf myhome_directory.tar.gz /home/linuxconfig

#!/bin/bash
 STRING="HELLO WORLD!!!"
 echo $STRING

#!/bin/bash
 OF=myhome_directory_$(date +%Y%m%d).tar.gz
 tar -czf $OF /home/linuxconfig

#!/bin/bash
#Define bash global variable
#This variable is global and can be used anywhere in this bash script
VAR="global variable"
function bash {
#Define bash local variable
#This variable is local to bash function only
local VAR="local variable"
echo $VAR
}
echo $VAR
bash
# Note the bash global variable did not change
# "local" is bash reserved word
echo $VAR

#!/bin/bash
#Define bash global variable
#This variable is global and can be used anywhere in this bash script
VAR="global variable"
function bash {
#Define bash local variable
#This variable is local to bash function only
local VAR="local variable"
echo $VAR
}
echo $VAR
bash
# Note the bash global variable did not change
# "local" is bash reserved word
echo $VAR

/arguments.sh Bash Scripting Tutorial

#!/bin/bash
# use backticks " ` ` " to execute shell command
echo `uname -o`
# executing bash command without backticks
echo uname -o

#!/bin/bash
 
echo -e "Hi, please type the word: \c "
read  word
echo "The word you entered is: $word"
echo -e "Can you please enter two words? "
read word1 word2
echo "Here is your input: \"$word1\" \"$word2\""
echo -e "How do you feel about bash scripting? "
# read command now stores a reply into the default build-in variable $REPLY
read
echo "You said $REPLY, I'm glad to hear that! "
echo -e "What are your favorite colours ? "
# -a makes read command to read into an array
read -a colours
echo "My favorite colours are also ${colours[0]}, ${colours[1]} and ${colours[2]}:-)"

#!/bin/bash
# bash trap command
trap bashtrap INT
# bash clear screen command
clear;
# bash trap function is executed when CTRL-C is pressed:
# bash prints message => Executing bash trap subrutine !
bashtrap()
{
    echo "CTRL+C Detected !...executing bash trap !"
}
# for loop from 1/10 to 10/10
for a in `seq 1 10`; do
    echo "$a/10 to Exit." 
    sleep 1;
done
echo "Exit Bash Trap Example!!!"

#!/bin/bash
#Declare array with 4 elements
ARRAY=( 'Debian Linux' 'Redhat Linux' Ubuntu Linux )
# get number of elements in the array
ELEMENTS=${#ARRAY[@]}
 
# echo each element in array 
# for loop
for (( i=0;i<$ELEMENTS;i++)); do
    echo ${ARRAY[${i}]}
done

#!/bin/bash
#Declare array
 declare -a ARRAY
#Open file for reading to array
exec 10
let count=0
 
while read LINE <&10; do
 
    ARRAY[$count]=$LINE
    ((count++))
done
 
echo Number of elements: ${#ARRAY[@]}
# echo array's content
echo ${ARRAY[@]}
# close file 
exec 10>&-

#!/bin/bash
directory="./BashScripting"
 
# bash check if directory exists
if [ -d $directory ]; then
	echo "Directory exists"
else 
	echo "Directory does not exists"
fi

#!/bin/bash
 
# Declare variable choice and assign value 4
choice=4
# Print to stdout
 echo "1. Bash"
 echo "2. Scripting"
 echo "3. Tutorial"
 echo -n "Please choose a word [1,2 or 3]? "
# Loop while the variable choice is equal 4
# bash while loop
while [ $choice -eq 4 ]; do
 
# read user input
read choice
# bash nested if/else
if [ $choice -eq 1 ] ; then
 
        echo "You have chosen word: Bash"
 
else                   
 
        if [ $choice -eq 2 ] ; then
                 echo "You have chosen word: Scripting"
        else
 
                if [ $choice -eq 3 ] ; then
                        echo "You have chosen word: Tutorial"
                else
                        echo "Please make a choice between 1-3 !"
                        echo "1. Bash"
                        echo "2. Scripting"
                        echo "3. Tutorial"
                        echo -n "Please choose a word [1,2 or 3]? "
                        choice=4
                fi   
        fi
fi
done

#!/bin/bash
# declare integers
NUM1=2
NUM2=2
if [ $NUM1 -eq $NUM2 ]; then
	echo "Both Values are equal"
else 
	echo "Values are NOT equal"
fi

#
#!/bin/bash
# declare integers
NUM1=2
NUM2=1
if [ $NUM1 -eq $NUM2 ]; then
	echo "Both Values are equal"
else 
	echo "Values are NOT equal"
fi

#!/bin/bash
# declare integers
NUM1=2
NUM2=1
if   [ $NUM1 -eq $NUM2 ]; then
	echo "Both Values are equal"
elif [ $NUM1 -gt $NUM2 ]; then
	echo "NUM1 is greater then NUM2"
else 
	echo "NUM2 is greater then NUM1"
fi

#!/bin/bash
#Declare string S1
S1="Bash"
#Declare string S2
S2="Scripting"
if [ $S1 = $S2 ]; then
	echo "Both Strings are equal"
else 
	echo "Strings are NOT equal"
fi

#!/bin/bash
#Declare string S1
S1="Bash"
#Declare string S2
S2="Bash"
if [ $S1 = $S2 ]; then
	echo "Both Strings are equal"
else 
	echo "Strings are NOT equal"
fi

#!/bin/bash
file="./file"
if [ -e $file ]; then
	echo "File exists"
else 
	echo "File does not exists"
fi

#!/bin/bash
 
while [ ! -e myfile ]; do
# Sleep until file does exists/is created
sleep 1
done

#!/bin/bash
 
# bash for loop
for f in $( ls /var/ ); do
	echo $f
done

$ for f in $( ls /var/ ); do echo $f; done

#!/bin/bash
COUNT=6
# bash while loop
while [ $COUNT -gt 0 ]; do
	echo Value of count is: $COUNT
	let COUNT=COUNT-1
done

#!/bin/bash
COUNT=0
# bash until loop
until [ $COUNT -gt 5 ]; do
        echo Value of count is: $COUNT
        let COUNT=COUNT+1
done

#!/bin/bash
# This bash script will locate and replace spaces
# in the filenames
DIR="."
# Controlling a loop with bash read command by redirecting STDOUT as
# a STDIN to while loop
# find will not truncate filenames containing spaces
find $DIR -type f | while read file; do
# using POSIX class [:space:] to find space in the filename
if [[ "$file" = *[[:space:]]* ]]; then
# substitute space with "_" character and consequently rename the file
mv "$file" `echo $file | tr ' ' '_'`
fi;
# end of while loop
done

!/bin/bash
# BASH FUNCTIONS CAN BE DECLARED IN ANY ORDER
function function_B {
        echo Function B.
}
function function_A {
        echo $1
}
function function_D {
        echo Function D.
}
function function_C {
        echo $1
}
# FUNCTION CALLS
# Pass parameter to function A
function_A "Function A."
function_B
# Pass parameter to function C
function_C "Function C."
function_D

#!/bin/bash
 
PS3='Choose one word: ' 
 
# bash select
select word in "linux" "bash" "scripting" "tutorial" 
do
  echo "The word you have selected is: $word"
# Break, otherwise endless loop
  break  
done
 
exit 0

#!/bin/bash
echo "What is your preferred programming / scripting language"
echo "1) bash"
echo "2) perl"
echo "3) phyton"
echo "4) c++"
echo "5) I do not know !"
read case;
#simple case bash structure
# note in this case $case is variable and does not have to
# be named case this is just an example
case $case in
    1) echo "You selected bash";;
    2) echo "You selected perl";;
    3) echo "You selected phyton";;
    4) echo "You selected c++";;
    5) exit
esac

#!/bin/bash
 
#Declare bash string variable
BASH_VAR="Bash Script"
 
# echo variable BASH_VAR
echo $BASH_VAR
 
#when meta character such us "$" is escaped with "\" it will be read literally
echo \$BASH_VAR 
 
# backslash has also special meaning and it can be suppressed with yet another "\"
echo "\\"

#!/bin/bash
 
 #Declare bash string variable
 BASH_VAR="Bash Script"
 
 # echo variable BASH_VAR
 echo $BASH_VAR
 
 # meta characters special meaning in bash is suppressed when  using single quotes 
 echo '$BASH_VAR  "$BASH_VAR"'

#!/bin/bash
 
#Declare bash string variable
BASH_VAR="Bash Script"
 
# echo variable BASH_VAR
echo $BASH_VAR
 
# meta characters and its special meaning in bash is 
# suppressed when using double quotes except "$", "\" and "`"
 
echo "It's $BASH_VAR  and \"$BASH_VAR\" using backticks: `date`"

#!/bin/bash
 
# as a example we have used \n as a new line, \x40 is hex value for @
# and \56 is octal value for .
echo $'web: www.linuxconfig.org\nemail: web\x40linuxconfig\56org'

#!/bin/bash
 
let RESULT1=$1+$2
echo $1+$2=$RESULT1 ' -> # let RESULT1=$1+$2'
declare -i RESULT2
RESULT2=$1+$2
echo $1+$2=$RESULT2 ' -> # declare -i RESULT2; RESULT2=$1+$2'
echo $1+$2=$(($1 + $2)) ' -> # $(($1 + $2))'

#!/bin/bash
 
echo '### let ###'
# bash addition
let ADDITION=3+5
echo "3 + 5 =" $ADDITION
 
# bash subtraction
let SUBTRACTION=7-8
echo "7 - 8 =" $SUBTRACTION 
 
# bash multiplication
let MULTIPLICATION=5*8
echo "5 * 8 =" $MULTIPLICATION
 
# bash division
let DIVISION=4/2
echo "4 / 2 =" $DIVISION
 
# bash modulus
let MODULUS=9%4
echo "9 % 4 =" $MODULUS
 
# bash power of two
let POWEROFTWO=2**2
echo "2 ^ 2 =" $POWEROFTWO
 
 
echo '### Bash Arithmetic Expansion ###'
# There are two formats for arithmetic expansion: $[ expression ] 
# and $(( expression #)) its your choice which you use
 
echo 4 + 5 = $((4 + 5))
echo 7 - 7 = $[ 7 - 7 ]
echo 4 x 6 = $((3 * 2))
echo 6 / 3 = $((6 / 3))
echo 8 % 7 = $((8 % 7))
echo 2 ^ 8 = $[ 2 ** 8 ]
 
 
echo '### Declare ###'
 
echo -e "Please enter two numbers \c"
# read user input
read num1 num2
declare -i result
result=$num1+$num2
echo "Result is:$result "
 
# bash convert binary number 10001
result=2#10001
echo $result
 
# bash convert octal number 16
result=8#16
echo $result
 
# bash convert hex number 0xE6A
result=16#E6A
echo $result

#!/bin/bash
# get floating point number
floating_point_number=3.3446
echo $floating_point_number
# round floating point number with bash
for bash_rounded_number in $(printf %.0f $floating_point_number); do
echo "Rounded number with bash:" $bash_rounded_number
done

#!/bin/bash
# Simple linux bash calculator 
echo "Enter input:" 
read userinput
echo "Result with 2 digits after decimal point:"
echo "scale=2; ${userinput}" | bc 
echo "Result with 10 digits after decimal point:"
echo "scale=10; ${userinput}" | bc 
echo "Result as rounded integer:"
echo $userinput | bc

#!/bin/bash
 
 echo "Redirect this STDOUT to STDERR" 1>&2

#!/bin/bash
 
 cat $1 2>&1

cat /proc/partitions

cat /proc/partitions > partitions.txt

grep -r hda6 * . 2> stderr.txt

grep -r hda6 * . 1>&2 stderr.txt

grep -r hda6 * . 2>&1 stderr.txt

grep -r hda6 * . &> stderr_and_stdout.txt

// 高精度延迟函数 【开发草稿】 Rev 0.01
/* 注：MSDN中提到的以下问题，本版本程序并未处理！！
On a multiprocessor computer, it should not matter which processor is called. 
However, you can get different results on different processors due to bugs 
in the basic input/output system (BIOS) or the hardware abstraction layer (HAL).
To specify processor affinity for a thread, use the SetThreadAffinityMask function. 
*/
int DelayPrecision(int TimeInMilliSecond)
{
    LARGE_INTEGER Frequency;
    LARGE_INTEGER CountBegin;
    LARGE_INTEGER CountNow;
    LONGLONG DelayCount;
    LONGLONG EndCount;
 
    if (0 != QueryPerformanceFrequency(&Frequency))
    {
        //试算终止计数
        DelayCount = Frequency.QuadPart / 1000 * TimeInMilliSecond;
        if (0 != QueryPerformanceCounter(&CountBegin))
        {
            EndCount = CountBegin.QuadPart + DelayCount;
            if (EndCount < CountBegin.QuadPart)
            {
                //计数器循环回去了
                while (1)
                {
                    if (0 != QueryPerformanceCounter(&CountNow))
                    {
                        if (CountNow.QuadPart < CountBegin.QuadPart && CountNow.QuadPart > EndCount)
                        {
                            return 1;
                        }
                    }
                    else
                    {
                        break;
                    }
                }
            }
            else
            {
                //一般情况
                while (1)
                {
                    if (0 != QueryPerformanceCounter(&CountNow))
                    {
                        if (CountNow.QuadPart > EndCount)
                        {
                            return 2;
                        }
                    }
                    else
                    {
                        break;
                    }
                }
            }
 
        }
 
    }
 
    //如果无法使用高精度定时器,拿Sleep凑合着用吧.
    Sleep(TimeInMilliSecond);
 
 
    return 0;
}

public class Ant
{
    public Square SQUARE;           //蚂蚁所在方格
    public Food CARRYING = null;    //所搬的食物数
    public int ID;                  //蚂蚁的编号
    public boolean HELPING = false; //是否帮忙搬运食物
 
public void move(int turn)
{
    //蚂蚁移动到下一个方格
}
}

public class Square
{ public Square NE;            //附近的8个方向的方格
 
     public Square N;
     public Square NW;
     public Square W;
     public Square SW;
     public Square S;
     public Square SE;
     public Square E;
     public LinkedList ANTS;        //本方格中包含的蚂蚁
     public Food FOOD;            //本方格中包含的食物数
     public Nest NEST;                //方格为蚁穴
     public Pheromone_1 PHEROMONE_1;            //本方格中的外激素含量
     public int X;            //本方格的坐标
     public int Y;
     private World WORLD;            //所属的环境
     public boolean WALL;            //是否有障碍物
 
    public Square(int x, int y, World world)
    {
        FOOD = null;
        NEST = null;
        PHEROMONE_1 = null;
        X = x;
        Y = y;
        WORLD = world;
        WALL = false;
        ANTS = new LinkedList();
    }

public class World
{
    private Square[][] WORLD;        //定义环境二维数组
    private int WIDTH;                //环境的长宽
    private int HEIGHT;
    private Pheromone_1List P1LIST;        //保存所有外激素的列表
 
    public World(Pheromone_1List p1list)
    {
        this.WIDTH = Settings.WIDTH;
        this.HEIGHT = Settings.HEIGHT;
        this.P1LIST = p1list;
        WORLD = new Square[WIDTH][HEIGHT];
    }

private Square chooseBestSquare()
{
     Square[] square_list = {SQUARE.E, SQUARE.NE, SQUARE.N, SQUARE.NW, SQUARE.W, SQUARE.SW, SQUARE.S, SQUARE.SE};
        double current_best_value = 0;
        double value = 0;
        Square square = SQUARE;
        // 选择最好的方格
 
        for(int i=0;i<square_list.length;i++)
        {
            value = calculateSquareValue(square_list[i]);//计算方格值
            if(value > current_best_value)
            {
                current_best_value = value;
                square = square_list[i];
            }
        }
        if(square.ANTS.size() >= Settings.MAXIMUM_NUMBER_OF_ANTS)
        {
          return SQUARE;
        }
        return square;
    }

private double calculateSquareValue(Square s)
{
    double[] thresholds = Settings.THRESHOLDS;
    if(s==null || s.WALL) // 方格有障碍物
    {
        return -100000;
    }
 
    // 计算方格中各项参数的值
    return s.getFood()*thresholds[0]        // 食物
    + s.getPheromone_1() * thresholds[1]    // 外激素
}

private void putPheromone_1(double amount)
{
    if(SQUARE.getPheromone_1() < Settings.PHEROMONE_LIMIT)
     SQUARE.addPheromone_1(amount);
}