此程序出自《Assembly Language step by step programming with linux》第12章，用于演示时间相关的libc库函数的使用，程序中使用了如下的libc库函数：
time_t time( time_t *timer );
char *ctime( const time_t *timer );
double difftime( time_t timer1, time_t timer0 );
struct tm *localtime( const time_t *timer );
int getchar( void );
程序如下：
[SECTION .data] ; Section containing initialised data
TimeMsg db "Hey, what time is it? It's %s",10,0
YrMsg db "The year is %d.",10,0
Elapsed db "A total of %d seconds has elapsed since program began running.",10,0
[SECTION .bss] ; Section containing uninitialized data
OldTime resd 1 ; Reserve 3 integers (doubles) for time values
NewTime resd 1
TimeDiff resd 1
TimeStr resb 40 ; Reserve 40 bytes for time string
TmCopy resd 9 ; Reserve 9 integer fields for time struct tm
[SECTION .text] ; Section containing code
extern ctime
extern difftime
extern getchar
extern printf
extern localtime
extern time
global main ; Required so linker can find entry point
main:
push ebp ; Set up stack frame for debugger
mov ebp,esp
push ebx ; Program must preserve EBP, EBX, ESI, & EDI
push esi
push edi
;;; Everything before this is boilerplate; use it for all ordinary apps!
; Generate a time_t calendar time value with clib's time function
push 0 ; Push a 32-bit null pointer to stack,
; since we don't need a buffer.
call time ; Returns calendar time in EAX
add esp,4 ; Clean up stack after call
mov [OldTime],eax ; Save time value in memory variable
; Generate a string summary of local time with clib's ctime function
push OldTime ; Push address of calendar time value
call ctime ; Returns pointer to ASCII time string in EAX
add esp,4 ; Stack cleanup for 1 parm
push eax ; Push pointer to ASCII time string on stack
push TimeMsg ; Push pointer to base message text string
call printf ; Merge and display the two strings
add esp,8 ; Stack cleanup: 2 parms X 4 bytes = 8
; Generate local time values into clib's static tm struct
push dword OldTime ; Push address of calendar time value
call localtime ; Returns pointer to static time structure in EAX
add esp,4 ; Stack cleanup for 1 parm
; Make a local copy of clib's static tm struct
mov esi,eax ; Copy address of static tm from eax to ESI
mov edi,TmCopy ; Put the address of the local tm copy in EDI
mov ecx,9 ; A tm struct is 9 dwords in size under Linux
cld ; Clear DF so we move up-memory
rep movsd ; Copy static tm struct to local copy
; Display one of the fields in the tm structure
mov edx,dword [TmCopy+20] ; Year field is 20 bytes offset into tm
add edx,1900 ; Year field is # of years since 1900
push edx ; Push value onto the stack
push YrMsg ; Push address of the base string
call printf ; Display string and year value with printf
add esp,8 ; Stack cleanup: 2 parms X 4 bytes = 8
; Wait a few seconds for user to press Enter so we have a time difference:
call getchar ; Wait for user to press Enter
; Calculating seconds passed since program began running:
push dword 0 ; Push null ptr; we'll take value in EAX
call time ; Get current time value; return in EAX
add esp,4 ; Clean up the stack
mov [NewTime],eax ; Save new time value
sub eax,[OldTime] ; Calculate time difference value
mov [TimeDiff],eax ; Save time difference value
push dword [TimeDiff] ; Push difference in seconds onto the stack
push Elapsed ; Push addr. of elapsed time message string
call printf ; Display elapsed time
add esp,8 ; Stack cleanup for 1 parm
;;; Everything after this is boilerplate; use it for all ordinary apps!
pop edi ; Restore saved registers
pop esi
pop ebx
mov esp,ebp ; Destroy stack frame before returning
pop ebp
ret ; Return control to Linux
程序分析：
push 0 //函数参数timer=NULL
call time //调用time函数，返回当前时间，用与1970年1月1日0点0分0秒的相差的秒数表示。
add esp,4 //清理栈
mov [OldTime],eax //保存返回值到OldTime变量
push OldTime // 函数参数timer= OldTime
call ctime //调用ctime函数，返回时间信息字符串
add esp,4 //清理栈
push eax //时间字符串压入堆栈
push TimeMsg //时间显示格式
call printf //调用printf函数，打印时间信息
add esp,8 //清理栈，因为两个参数，所以加8
push dword OldTime //函数参数 timer= OldTime
call localtime //调用localtime函数，对时间值进行转换，返回tm结构体的指针。
add esp,4 //清理栈
mov esi,eax //esi是源，保存返回的tm结构体的地址
mov edi,TmCopy //edi=TmCopy，指定拷贝的目的地址
mov ecx,9 //ecx用于循环计数，tm结构体是9个dword，因此ecx=9
cld //清除DF标志，控制地址变化方向从低到高
rep movsd //进行拷贝，把返回的tm结构体拷贝到TmCopy
mov edx,dword [TmCopy+20] //edx=TmCopy的year字段
add edx,1900 //因为tm保存的是与1900年的差值，因此要加1900
push edx //把年份参数压入堆栈
push YrMsg //格式化字符串
call printf //调用printf函数打印年份信息
add esp,8 //清理栈
call getchar //等待用户键入回车键
push dword 0 //函数参数timer=NULL
call time //调用time函数，返回当前时间。
add esp,4 //清理栈
mov [NewTime],eax //把当前时间值保存到NewTime中。
sub eax,[OldTime] //用NewTime- OldTime的值放入eax
mov [TimeDiff],eax //差值保存到TimeDiff中
push dword [TimeDiff] //把差值作为函数参数，压入堆栈
push Elapsed //格式化字符串压入堆栈
call printf //调用printf函数，显示消耗的秒数信息。
add esp,8 //清理栈
makefile文件内容：
timetest: timetest.o
gcc timetest.o -o timetest
timetest.o: timetest.asm
nasm -f elf -g -F stabs timetest.asm
测试：
[root@bogon timetest]# make
nasm -f elf -g -F stabs timetest.asm
gcc timetest.o -o timetest
[root@bogon timetest]# ./timetest
Hey, what time is it? It's Wed Jan 14 15:12:39 2015
The year is 2015.
A total of 2 seconds has elapsed since program began running.