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±ê Ìâ: [תÔØ]unix»·¾³¸ß¼¶±à³Ì-¸½C
·¢ÐÅÕ¾: BBS ˮľÇ廪վ (Wed Mar 15 14:32:37 2000)
·¢ÐÅÈË: taosm (128+64-->cool), ÐÅÇø: unix
±ê Ìâ: unix»·¾³¸ß¼¶±à³Ì--¸½Â¼C Ï°Ìâ´ð°¸
·¢ÐÅÕ¾: Î÷Ê®°ËBBS (Sat Mar 11 14:37:49 2000), תÐÅ
¸½Â¼C Ï°Ìâ´ð°¸
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µÄËùÓÐÎļþ¡£
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$ ls -ldi /etc/. /etc/..
3077 drwxr-sr-x 7 bin 2048 Aug 5 20:12 /etc/./
2 drwxr-xr-x 13 root 512 Aug 5 20:11 /etc/../
$ls -ldi /. /..
2 drwxr-xr-x 13 root 512 Aug 5 20:11 /./
2 srwxr-xr-x 13 root 512 Aug 5 20:11 /../ {.ºÍ..µÄµÄi½ÚµãÊý¾ùΪ2
µÄi½ÚµãÊý¾ùΪ2
1.3 ¼ÙÈçperrorµÄptr²ÎÊýÊÇÒ»¸öÖ¸Õ룬Ôòperror¾Í¿ÉÒԸıäptrËùÖ¸´®µÄÄÚÈÝ¡£Ëù
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¾ÍûÓбØҪʹÓÃconstÊôÐÔ¡£
1.4 µ÷ÓÃfflush£¬fprintfºÍvprintfº¯Êý»á¸Ä±äerrnoµÄÖµ¡£Èç¹ûËüµÄÖµ±äÁ˵«Ã»
Óб£´æ£¬Ôò×îÖÕÏÔʾµÄ´íÎóÐÅÏ¢ÊDz»ÕýÈ·µÄ¡£
ÔÚ¹ýÈ¥¿ª·¢Ðí¶à³ÌÐòÖж¼¿ÉÒÔ·¢ÏÖ²»±£´æerrnoµÄÇé¿ö£¬µäÐ͵ĴòÓ¡³öµÄ´íÎóÐÅÏ¢
ÊÇ"Not a typewriter."¡£ÔÚ5.4½ÚÖбê×¼I/O¿â¸ù¾Ý±ê×¼I/OÁ÷ÊÇ·ñÖ¸ÏòÖÕ¶ËÉ豸¶ø
¸Ä±äÁ÷µÄ»º´æÆ÷¡£istty(11.9½Ú)ͨ³£ÓÃÀ´ÅжÏÁ÷ÊÇ·ñÖ¸ÏòÖÕ¶ËÉ豸£¬Èç¹ûÁ÷²»Ö¸
ÏòÖÕ¶ËÉ豸£¬errno¿ÉÄÜÖÃΪENOTTY£¬´Ó¶øÒýÆð¸Ã´íÎó¡£³ÌÐòC.1±íÏÖÁËÕâ¸öÊôÐÔ¡£
#include <stdio.h>
/*
* The following prints errno=25 (ENOTTY) under 4.3BSD and SVR2,
* when stdout is redirected to a file.
* Under SVR4 and 44BSD it works OK.
*/
int
main()
{
int fd;
extern int errno;
if ( (fd = open("/no/such/file", 0)) < 0) {
printf("open error: ");
printf("errno = %d\n", errno);
}
exit(0);
}
³ÌÐò C.1 errnoºÍprintfµÄ½»»¥×÷ÓÃ
Ö´ÐÐÉÏÃæµÄ³ÌÐò£¬½á¹ûΪ£º
$ grep BSD /etc/motd
4.3 BSD UNIX #29: Thu Mar 29 11:14:13 MST 1990
$ a.out
open error: error = 2 {¹¤×÷Õý³££¬stdoutÊÇÒ»¸öÖÕ¶Ë}
$ a.out > temp.foo
$ cat temp.foo
open error: error = 25 {´íÎó}
1.5 2038Äê¡£
1.6 ´óÔ¼248Ìì¡£
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2.1 ÏÂÃæÊÇ4.3+BSDÖÐʹÓõļ¼Êõ¡£ÔÚ<machine/ansi.h> ÖУ¬Óôóд×Öĸ¶¨Òå¿ÉÒÔ
ÔÚ¶à¸öÍ·ÎļþÖгöÏֵĻù±¾Êý¾ÝÀàÐÍ¡£ÀýÈ磺
#ifndef _ANSI_--H_
#define _ANSI_H_
#define _CLOCK_T_ unsigned long
#define _SIZE_T_ unsigned int
¡
#endif /*_ANSI_H_*/
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#ifdef _SIZE_T_
typedef _SIZE_T_ size_t;
#undef _SIZE_T_
#endif
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3.1 ËùÓеĴÅÅÌI/O¶¼Òª¾¹ýÄں˵Ŀ黺´æÆ÷£¬Î¨Ò»ÀýÍâµÄÊǶÔÔʼ´ÅÅÌÉ豸µÄI/
O£¬µ«ÊÇÎÒÃDz»¿¼ÂÇÕâÖÖÇé¿ö(Bach [1986] ÖеĵÚÈýÕ½²ÊöÁËÕâÖÖ»º´æÆ÷µÄ²Ù×÷)
¡£¼ÈÈ»read»òwriteµÄÊý¾Ý¶¼Òª±»Äں˻º´æ£¬ÄÇôÊõÓï"ÎÞ»º´æ×°ÖõÄI/O"Ö¸µÄÊÇÔÚ
Óû§µÄ½ø³ÌÖжÔÕâÁ½¸öº¯Êý²»»á×Ô¶¯»º´æ£¬Ã¿´Îread»òwrite¾ÍÒª½øÐÐÒ»´Îϵͳµ÷
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3.3 ÿ´Îµ÷ÓÃopenº¯Êý¾Í·ÖÅäÒ»¸öÎļþ±íÏÈç¹ûÁ½´Î´ò¿ªµÄÊÇÏàͬµÄÎļþ£¬ÔòÁ½
¸öÎļþ±íÏîÖ¸ÏòÏàͬµÄv½Úµã¡£µ÷ÓÃdupÒýÓÃÒÑ´æÔÚµÄÎļþ±íÏî(´Ë´¦Ö¸fd1µÄÎļþ±í
Ïî)£¬¼ûͼC.1¡£µ±F_SETFD×÷ÓÃÓÚfd1ʱ£¬Ö»Ó°Ïìfd1µÄÎļþÃèÊö·û±êÖ¾£»F_SETFL×÷
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3.4 Èç¹ûfdÊÇ1£¬Ö´ÐÐdup2(fd£¬1)ºó·µ»Ø1£¬µ«ÊÇûÓйرÕÃèÊö·û1(²Î¼û3.12½Ú)¡£
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3.5 shellÊÇ´Ó×óµ½ÓÒ´¦ÀíÃüÁîÐÐ,ËùÒÔ
a.out > outfile 2 >&1
Ê×ÏÈÉèÖñê×¼Êä³öµ½outfile£¬È»ºóÖ´ÐÐdups½«±ê×¼Êä³ö¸´ÖƵ½ÃèÊö·û2(±ê×¼´íÎó
)ÉÏ£¬Æä½á¹ûÊǽ«±ê×¼Êä³öºÍ±ê×¼´íÎóÉèÖÃΪÏàͬµÄÎļþ£¬¼´ÃèÊö·û1ºÍ2Ö¸ÏòÏàͬ
µÄÎļþ±íÏî¡£
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a.out 2 > &1 >outfile
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±íÏî¡£
3.6 ÕâÖÖÇé¿ö֮ϣ¬ÈÔÈ»¿ÉÒÔÓÃlseekºÍreadº¯Êý¶ÁÎļþÖÐÈκÎÒ»´¦µÄÄÚÈÝ¡£µ«ÊÇ
writeº¯ÊýÔÚдÊý¾Ý֮ǰ»á×Ô¶¯½«ÎļþÆ«ÒÆÁ¿ÉèÖÃΪÎļþ⣬ËùÒÔдÎļþʱֻÄÜ´Ó
Îļþβ¿ªÊ¼£¬²»ÄÜÔÚÈÎÒâλÖá£
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4.1 statº¯Êý×ÜÊÇ˳һ¸ö·ûºÅÁ¬½ÓÏòÇ°£¬ËùÒÔÐ޸ĺóµÄ³ÌÐò²»»áÏÔʾÎļþÀàÐÍÊÇ"
·ûºÅÁ¬½Ó"¡£ÀýÈ磺/binÊÇ/usr/binµÄÒ»¸ö·ûºÅÁ¬½Ó£¬µ«ÊÇstatº¯ÊýµÄ½á¹ûÖ»ÏÔʾ
/binÊÇÒ»¸öĿ¼£¬¶ø²»ËµÃ÷ËüÊÇÒ»¸ö·ûºÅÁ¬½Ó¡£ÈôÒ»¸ö·ûºÅÁ¬½ÓÖ¸ÏòÒ»²»´æÔÚµÄÎÄ
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4.2 ½«ÏÂÃæµÄ¼¸ÐÐÓï¾ä¼ÓÈë<ourhdr.h>
#if defined ( S_IFLNK ) && !defined ( S_ISLNK )
#define S_ISLNK ( mode ) ((( mode ) & S_IFMT ) == S_IFLNK )
#endif
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4.3 ¹Ø±ÕÁ˸ÃÎļþµÄËùÓдæȡȨÏÞ¡£
$ umask 777
$ data > temp.foo
$ ls -l temp.foo
---------- l stevens 29 Jan 14
6:39 temp.foo
4.4 ÏÂÃæµÄÃüÁî±íʾ¹Ø±ÕÓû§¶ÁȨÏÞµÄÇé¿ö¡£
$ data > foo
$ chmod u-r foo {¹Ø±ÕÓû
¶ÁȨÏÞ}
$ ls -l foo
ÑéÖ¤ÎļþµÄȨÏÞ}
--w-rw-r-- l stevens 29 Jul 31 09:00
oo
$ cat foo
{¶ÁÎļþ}
cat: foo: Permission denied
4.5 Èç¹ûÓÃopen»òcreat´´½¨ÒѾ´æÔÚµÄÎļþ£¬Ôò¸ÃÎļþµÄ´æȡȨÏÞ²»±ä¡£Í¨¹ý³Ì
Ðò4.3¿ÉÒÔÑéÖ¤Õâµã¡£
$ rm foo bar
ɾ³ýÎļþ}
$ data > foo
´´½¨Îļþ}
$ data > bar
$ chmod a-r foo bar {¹Ø±ÕËùÓ
µÄ¶ÁȨÏÞ}
$ ls -l foo bar {ÑéÖ¤ÆäÈ
ÏÞ}
--w--w---- l stevens 29 Jul 31 10:47
ar
--w--w---- l stevens 29 Jul 31 10:47
oo
$ a.out
ÔËÐгÌÐò4.3}
$ ls -l foo bar {¼ì²éÎļþµÄȨÏÞº
´óС}
--w--w---- l stevens 0 Jul 31 10:47 bar
--w--w---- l stevens 0 Jul 31 10:47
oo
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4.8 µ±´´½¨ÐµÄcoreÎļþʱ£¬Äں˶ÔÆä´æȡȨÏÞÓÐÒ»¸öĬÈÏÉèÖã¬ÔÚ±¾ÀýÖÐÊÇ£ºr
w-r--r--¡£Õâһȱʡֵ¿ÉÄÜ»áÒ²Ðí²»»á±»umaskµÄÖµÐ޸ġ£Shell¶Ô´´½¨µÄÖض¨ÏòµÄ
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kÐ޸ģ¬ÔÚ±¾ÀýÖÐumaskΪ02¡£
4.9 ²»ÄÜʹÓÃduµÄÔÒòÊÇËüÐèÒªÎļþÃû»òĿ¼Ãû×÷Ϊ²ÎÊý£¬ÀýÈ磺
du tempfile
du .
Ö»Óе±unlinkº¯Êý·µ»Øʱ²ÅÊÍ·ÅtempfileµÄĿ¼ÏduÃüÁîûÓмÆËãÈÔÈ»±»temp
fileÕ¼ÓõĿռ䡣ÔÚ±¾ÀýÖÐÖ»ÄÜʹÓÃdfÃüÁî²ì¿´ÎļþϵͳÖÐʵ¼Ê¿ÉÓõÄ×ÔÓɿռ䡣
4.10 Èç¹û±»unlinkµÄÁ´½Ó²»ÊǸÃÎļþµÄ×îºóÒ»¸öÁ´½Ó£¬¸ÃÎļþ²»»áɾ³ý¡£´Ëʱ£¬
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4.11 ÓÃopendir´ò¿ªÒ»¸öĿ¼ºó£¬Ñ»·µ÷Óú¯Êýdopath¡£¼ÙÉèopendirʹÓÃÒ»¸öÎÄ
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4.13 chrootº¯ÊýÓÃÓÚ¸¨ÖúInternetÎļþ´«Êä³ÌÐò(FTP)ÖеݲȫÐÔ¡£ÏµÍ³ÖÐûÓÐÕÊ
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4.16 ¶ÔcpioÀ´Ëµ£¬¼È¿ÉÒԸıäÎļþµÄ·ÃÎÊʱ¼ä(st_atime)ºÍÐÞ¸Äʱ¼ä(st_mtime)
Ò²¿ÉÒÔ¶¼²»¸Ä±ä¡£cpioµÄ-aÑ¡Ïî¿ÉÒÔÔÚ¶ÁÎļþºóÖØÐÂÉèÖÃÎļþµÄ·ÃÎÊʱ¼äΪ¶ÁÎļþ
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4.17 read¸Ä±äÁËÎļþ·ÃÎÊʱ¼ä£¬ÎªÁËÏû³ýÕâÒ»Ó°Ï죬ÓÐЩ°æ±¾µÄfile(1)µ÷ÓÃuti
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4.18 Äں˶ÔĿ¼µÄÉî¶ÈûÓÐÄÚÔÚµÄÏÞÖÆ£¬µ«ÊÇÈç¹û·¾¶ÃûµÄ³¤¶È³¬³öÁËPATH_MAX
ÓÐÐí¶àÃüÁî»áʧ°Ü¡£³ÌÐòC.2´´½¨ÁËÒ»¸öÉî¶ÈΪ100µÄĿ¼Ê÷£¬Ã¿Ò»¼¶Ä¿Â¼ÃûÓÐ45¸ö
×Ö·û¡£ÀûÓÃgetcwd¿ÉÒԵõ½µÚ100¼¶Ä¿Â¼µÄ¾ø¶Ô·¾¶Ãû(ÐèÒª¶à´Îµ÷ÓÃreallocÉêÇë
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#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "ourhdr.h"
#define DEPTH 100 /* directory depth */
#define MYHOME "/home/stevens"
#define NAME "alonglonglonglonglonglonglonglonglonglongname"
int
main(void)
{
int i, size;
char *path;
if (chdir(MYHOME) < 0)
err_sys("chdir error");
for (i = 0; i < DEPTH; i++) {
if (mkdir(NAME, DIR_MODE) < 0)
err_sys("mkdir failed, i = %d", i);
if (chdir(NAME) < 0)
err_sys("chdir failed, i = %d", i);
}
if (creat("afile", FILE_MODE) < 0)
err_sys("creat error");
/*
* The deep directory is created, with a file at the leaf.
* Now let's try and obtain its pathname.
*/
path = path_alloc(&size);
for ( ; ; ) {
if (getcwd(path, size) != NULL)
break;
else {
err_ret("getcwd failed, size = %d", size);
size += 100;
if ( (path = realloc(path, size)) == NULL)
err_sys("realloc error");
}
}
printf("length = %d\n%s\n", strlen(path), path);
exit(0);
}
³ÌÐòC.2 ´´½¨Éî¶ÈĿ¼
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$ a.out
getcwd failed, size = 1025: Result too large
getcwd failed, size = 1125: Result too large
¡ { 33ÐÐ}
getcwd failed, size = 4525: Result too large
length = 4613
{ÏÔʾ4613×ֽڵķ¾¶Ãû}
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5.3 µ±printfûÓÐÊä³öÈκÎ×Ö·ûʱ£¬È磺printf("") £¬·µ»Ø0¡£
5.4 ÕâÊÇÒ»¸ö±È½Ï³£¼ûµÄ´íÎó¡£getcÒÔ¼°getcharµÄ·µ»ØÖµÊÇÕûÐÍ£¬¶ø²»ÊÇ×Ö·ûÐÍ
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5.5 5¸ö×Ö·û³¤µÄǰ׺¡¢4¸ö×Ö·û³¤µÄ½ø³ÌÄÚΨһ±êʶÔÙ¼Ó5¸ö×Ö·û³¤µÄϵͳÄÚΨһ
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5.6 ʹÓ÷½·¨Îª£ºÏȵ÷ÓÃfflushºóµ÷ÓÃfsync£¬fsyncËùʹÓõIJÎÊýÓÉfilenoº¯Êý»ñ
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5.7 µ±³ÌÐò½»»¥ÔËÐÐʱ£¬±ê×¼ÊäÈëÊä³öÉ豸¾ùΪÐлº³å·½Ê½¡£Ã¿´Îµ÷ÓÃfgetsʱ±ê
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6.1 ÔÚSVR4ϵͳÖУ¬Óû§ÊÖ²áÖн²ÊöÁË»ñÈ¡ÒõÓ°ÃÜÂëÎļþµÄº¯Êý¡£ÎÒÃDz»ÄÜʹÓÃ6
.2½ÚËùÊöº¯Êý·µ»ØµÄpw_passwd±äÁ¿À´±È½Ï¼ÓÃܵĿÚÁî¡£ÕýÈ·µÄ·½·¨ÊÇʹÓÃÒõÓ°ÃÜ
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ÔÚ4.3+ BSDϵͳÖУ¬ÃÜÂëÎļþµÄÒõÓ°ÊÇ×Ô¶¯½¨Á¢µÄ¡£½öµ±µ÷ÓÃÕßµÄÓû§IDΪ0ʱ£¬
getpwnam»ògetpwuidº¯Êý·µ»ØµÄpassed½á¹¹ÖеÄpw_passwd×ֶβŰüº¬ÓмÓÃܵĿÚ
Áî¡£
6.2 ÔÚSVR4ϵͳÖУ¬³ÌÐòC.3½«Êä³ö¼ÓÃܵĿÚÁî¡£µ±È»£¬³ý·ÇÓг¬¼¶Óû§È¨ÏÞ£¬·ñ
Ôòµ÷ÓÃgetspnam½«·µ»ØEACCESS´íÎó¡£
#include <sys/types.h>
#include <shadow.h>
#include "ourhdr.h"
int
main(void) /* SVR4 version */
{
struct spwd *ptr;
if ( (ptr = getspnam("stevens")) == NULL)
err_sys("getspnam error");
printf("sp_pwdp = %s\n",
ptr->sp_pwdp == NULL || ptr->sp_pwdp[0] == 0 ?
"(null)" : ptr->sp_pwdp);
exit(0);
}
³ÌÐòC.3 ÔÚSVR4ϵͳÖÐÊä³ö¼ÓÃܵĿÚÁî
ÔÚ4.3+ BSDϵͳÖУ¬¾ßÓг¬¼¶Óû§È¨ÏÞʱ£¬³ÌÐòC.4½«Êä³ö¼ÓÃܵĿÚÁî¡£·ñÔòpw_
passedµÄ·µ»ØֵΪÐǺÅ(*)¡£
#include <sys/types.h>
#include <pwd.h>
#include "ourhdr.h"
int
main(void) /* 44BSD version */
{
struct passwd *ptr;
if ( (ptr = getpwnam("stevens")) == NULL)
err_sys("getpwnam error");
printf("pw_passwd = %s\n",
ptr->pw_passwd == NULL || ptr->pw_passwd[0] == 0
?
"(null)" : ptr->pw_passwd);
exit(0);
}
³ÌÐòC.4 ÔÚ4.3+ BSDϵͳÖÐÊä³ö¼ÓÃܵĿÚÁî
6.4
#include <time.h>
#include "ourhdr.h"
int
main(void)
{
time_t caltime;
struct tm *tm;
char line[MAXLINE];
if ( (caltime = time(NULL)) == -1)
err_sys("time error");
if ( (tm = localtime(&caltime)) == NULL)
err_sys("localtime error");
if (strftime(line, MAXLINE, "%a %b %d %X %Z %Y\n", tm) == 0)
err_sys("strftime error");
fputs(line, stdout);
exit(0);
}
³ÌÐòC.5 ÒÔdate(1)µÄ¸ñʽÊä³öÈÕÆÚºÍʱ¼ä
³ÌÐòC.5µÄÔËÐнá¹ûÈçÏ£º
$ echo $TZ
MST7
$ a.out
Wed Jan 15 06:48:57 MST 1992
$ TZ=EST5EDT a.out U.S.East Coast
Wed Jan 15 08:49:06 EST 1992
$ TZ=JST-9 a.out Japan
Wed Jan 15 22:49:12 JST 1992
µÚÆßÕÂ
7.1 ÔÒòÔÚÓÚprintfµÄ·µ»ØÖµ(Êä³öµÄ×Ö·ûÊý)±ä³ÉÁËmainº¯ÊýµÄ·µ»ØÂë¡£µ±È»£¬²¢
²»ÊÇËùÓеÄϵͳ¶¼»á³öÏÖ¸ÃÇé¿ö¡£
7.2 µ±³ÌÐò´¦ÓÚ½»»¥ÔËÐз½Ê½Ê±£¬±ê×¼Êä³öÉ豸ͨ³£´¦ÓÚÐлº³å·½Ê½£¬ËùÒÔµ±¼üÈë
ÐÂÐзûʱ£¬ÉϴεĽá¹û²Å±»ÕæÕýÊä³ö¡£Èç¹û±ê×¼Êä³öÉ豸±»¶¨Ïòµ½Ò»¸öÎļþ¶ø´¦ÓÚ
ÍêÈ«»º³å·½Ê½£¬Ôòµ±±ê×¼I/OÇåÀí²Ù×÷Ö´ÐÐʱ£¬½á¹û²ÅÕæÕý±»Êä³ö¡£
7.3 ÓÉÓÚagrcºÍargv²»ÏóenvironÒ»Ñù±£´æÔÚÈ«¾Ö±äÁ¿ÖУ¬ËùÒÔÔÚ´ó¶àÊýUnixϵͳ
ÖÐûÓÐÆäËü°ì·¨¡£
7.4 µ±C³ÌÐò¸´ÒýÓÃÒ»¸ö¿ÕÖ¸Õë³ö´íʱ£¬Ö´ÐиóÌÐòµÄ½ø³Ì½«ÖÕÖ¹£¬ÓÚÊÇ¿ÉÒÔÀûÓÃ
ÕâÖÖ·½·¨ÖÕÖ¹½ø³Ì¡£
7.5 ¶¨ÒåÈçÏ£º
typedef void Exitfunc ( void ) ;
int atexit ( Exitfunc *func ) ;
7.6 calloc½«·ÖÅäµÄÄÚ´æ¿Õ¼ä³õʼ»¯Îª0¡£µ«ÊÇANSI C²¢²»±£Ö¤0ÖµÓ븡µã0»ò¿ÕÖ¸
ÕëµÄÖµÏàͬ¡£
7.7 Ö»ÓÐͨ¹ýexecº¯ÊýÖ´ÐÐÒ»¸ö³ÌÐòʱ£¬²Å»á·ÖÅä¶ÑºÍ¶ÑÕ»¡£
7.8 ¿ÉÖ´ÐÐÎļþ°üº¬ÁËÓÃÓÚµ÷ÊÔcoreÎļþµÄ·ûºÅ±íÐÅÏ¢£¬ÓÃstrip(1)¿ÉÒÔɾ³ýÕâЩ
ÐÅÏ¢£¬¶ÔÁ½¸öa.outÎļþÖ´ÐÐÕâÌõÃüÁËüÃǵĴóС¼õΪ98304ºÍ16384¡£
7.9 ûÓÐʹÓù²Ïí¿âʱ£¬¿ÉÖ´ÐÐÎļþµÄ´ó²¿·Ö¶¼±»±ê×¼I/O¿âËùÕ¼Óá£
7.10 Õâ¶Î´úÂë²»ÕýÈ·¡£ÒòΪÔÚifÓï¾äÖж¨ÒåÁË×Ô¶¯±äÁ¿val£¬ËùÒÔµ±ifÖеĸ´ºÏÓï
¾ä½áÊøʱ£¬¸Ã±äÁ¿¾Í²»´æÔÚÁË£¬µ«ÊÇÔÚifÓï¾äÖ®ÍâÓÖÓÃÖ¸ÕëÒýÓÃÒѾ²»´æÔÚµÄ×Ô¶¯
±äÁ¿val¡£
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7.1 ÔÒòÔÚÓÚprintfµÄ·µ»ØÖµ(Êä³öµÄ×Ö·ûÊý)±ä³ÉÁËmainº¯ÊýµÄ·µ»ØÂë¡£µ±È»£¬²¢
²»ÊÇËùÓеÄϵͳ¶¼»á³öÏÖ¸ÃÇé¿ö¡£
7.2 µ±³ÌÐò´¦ÓÚ½»»¥ÔËÐз½Ê½Ê±£¬±ê×¼Êä³öÉ豸ͨ³£´¦ÓÚÐлº³å·½Ê½£¬ËùÒÔµ±¼üÈë
ÐÂÐзûʱ£¬ÉϴεĽá¹û²Å±»ÕæÕýÊä³ö¡£Èç¹û±ê×¼Êä³öÉ豸±»¶¨Ïòµ½Ò»¸öÎļþ¶ø´¦ÓÚ
ÍêÈ«»º³å·½Ê½£¬Ôòµ±±ê×¼I/OÇåÀí²Ù×÷Ö´ÐÐʱ£¬½á¹û²ÅÕæÕý±»Êä³ö¡£
7.3 ÓÉÓÚagrcºÍargv²»ÏóenvironÒ»Ñù±£´æÔÚÈ«¾Ö±äÁ¿ÖУ¬ËùÒÔÔÚ´ó¶àÊýUnixϵͳ
ÖÐûÓÐÆäËü°ì·¨¡£
7.4 µ±C³ÌÐò¸´ÒýÓÃÒ»¸ö¿ÕÖ¸Õë³ö´íʱ£¬Ö´ÐиóÌÐòµÄ½ø³Ì½«ÖÕÖ¹£¬ÓÚÊÇ¿ÉÒÔÀûÓÃ
ÕâÖÖ·½·¨ÖÕÖ¹½ø³Ì¡£
7.5 ¶¨ÒåÈçÏ£º
typedef void Exitfunc ( void ) ;
int atexit ( Exitfunc *func ) ;
7.6 calloc½«·ÖÅäµÄÄÚ´æ¿Õ¼ä³õʼ»¯Îª0¡£µ«ÊÇANSI C²¢²»±£Ö¤0ÖµÓ븡µã0»ò¿ÕÖ¸
ÕëµÄÖµÏàͬ¡£
7.7 Ö»ÓÐͨ¹ýexecº¯ÊýÖ´ÐÐÒ»¸ö³ÌÐòʱ£¬²Å»á·ÖÅä¶ÑºÍ¶ÑÕ»¡£
7.8 ¿ÉÖ´ÐÐÎļþ°üº¬ÁËÓÃÓÚµ÷ÊÔcoreÎļþµÄ·ûºÅ±íÐÅÏ¢£¬ÓÃstrip(1)¿ÉÒÔɾ³ýÕâЩ
ÐÅÏ¢£¬¶ÔÁ½¸öa.outÎļþÖ´ÐÐÕâÌõÃüÁËüÃǵĴóС¼õΪ98304ºÍ16384¡£
7.9 ûÓÐʹÓù²Ïí¿âʱ£¬¿ÉÖ´ÐÐÎļþµÄ´ó²¿·Ö¶¼±»±ê×¼I/O¿âËùÕ¼Óá£
7.10 Õâ¶Î´úÂë²»ÕýÈ·¡£ÒòΪÔÚifÓï¾äÖж¨ÒåÁË×Ô¶¯±äÁ¿val£¬ËùÒÔµ±ifÖеĸ´ºÏÓï
¾ä½áÊøʱ£¬¸Ã±äÁ¿¾Í²»´æÔÚÁË£¬µ«ÊÇÔÚifÓï¾äÖ®ÍâÓÖÓÃÖ¸ÕëÒýÓÃÒѾ²»´æÔÚµÄ×Ô¶¯
±äÁ¿val¡£
µÚ°ËÕÂ
8.1 ÓÃÏÂÃ漸ÐдúÌæ³ÌÐò8.2Öе÷ÓÃprintfµÄÓï¾ä¡£
i = printf ("pid = %d, glob = %d, var = %d\n", getpid( ), glob, var);
sprintf (buf, "%d\n", i);
write (STDOUT_FILENO, buf, strlen(buf));
×¢ÒâÒª¶¨Òå±äÁ¿iºÍbuf¡£
ÕâÀï¼ÙÉè×Ó½ø³Ìµ÷ÓÃexitʱֻ¹Ø±Õ±ê×¼I/OÁ÷£¬²¢²»¹Ø±ÕÓë±ê×¼Êä³öÏà¹ØµÄÎļþÃè
Êö·ûSTDOUT_FILENO¡£ÓÐЩ°æ±¾µÄ±ê×¼I/O¿â»á¹Ø±ÕÓë±ê×¼Êä³öÏà¹ØµÄÎļþÃèÊö·û´Ó
¶øÒýÆðдʧ°Ü£¬ÕâÖÖÇé¿ö¾Íµ÷ÓÃdup½«±ê×¼Êä³ö¸´ÖƵ½ÁíÒ»¸öÃèÊö·û£¬writeÔòʹÓÃ
и´ÖƵÄÎļþÃèÊö·û¡£
8.2 ÎÒÃÇ¿ÉÒÔͨ¹ý³ÌÐòC.6À´ËµÃ÷Õâ¸öÎÊÌâ¡£
#include <sys/types.h>
#include "ourhdr.h"
static void f1(void), f2(void);
int
main(void)
{
f1();
f2();
_exit(0);
}
static void
f1(void)
{
pid_t pid;
if ( (pid = vfork()) < 0)
err_sys("vfork error");
/* child and parent both return */
}
static void
f2(void)
{
char buf[1000]; /* automatic variables */
int i;
for (i = 0; i < sizeof(buf); i++)
buf[i] = 0;
}
³ÌÐòC.6 ´íÎóʹÓÃvforkµÄÀý×Ó
ͼC.2 µ÷ÓÃvforkʱµÄÕ»Ö¡
µ±º¯Êýf1µ÷ÓÃvforkʱ£¬¸¸½ø³ÌµÄ¶ÑÕ»Ö¸Õë¾ÍÖ¸Ïòf1µÄÕ»Ö¡£¬¼ûͼC.2¡£vforkʹµÃ
×Ó½ø³ÌÏÈÖ´ÐÐÈ»ºó´Óf1·µ»Ø£¬½Ó×Å×Ó½ø³Ìµ÷ÓÃf2²¢ÇÒ¸²¸ÇÁËf1µÄ¶ÑÕ»Çø¼ä£¬ÔÚf2ÖÐ
×Ó½ø³Ì½«×Ô¶¯±äÁ¿bufµÄÖµÖÃΪ0£¬¼´½«¶ÑÕ»ÖеÄ1000¸ö×Ö½ÚµÄÖµ¶¼ÖÃΪ0¡£´Óf2·µ
»Øºó¸¸½ø³Ì¼ÌÐøÖ´Ðе÷ÓÃ_exit£¬Õâʱ¶ÑÕ»ÖÐmainÒÔϵÄÄÚÈÝÒѾ±»f2ÐÞ¸ÄÁË£¬µ«
ÊǸ¸½ø³ÌÈÔÈ»ÒÔΪµ÷ÓÃÁËvforkºó´Óf1·µ»Ø¡£·µ»ØÐÅÏ¢ËäÈ»±£´æÔÚ¶ÑÕ»ÖУ¬µ«ÊÇ¿É
ÄÜÒѾ±»×Ó½ø³ÌÐÞ¸ÄÁË¡£¶ÔÕâ¸öÀý×Ó£¬¸¸½ø³Ì¼ÌÐøÖ´ÐеĽá¹ûÒªÒÀÀµÓÚʵ¼ÊµÄUni
xϵͳ¡£(È磺·µ»ØÐÅÏ¢±£´æÔÚ¶ÑÕ»µÄ¾ßÌåλÖã¬Ð޸Ķ¯Ì¬±äÁ¿Ê±¸²¸ÇÁËÄÄЩÐÅÏ¢µÈ
µÈ¡£)ͨ³£µÄ½á¹ûÊÇÒ»¸öcoreÎļþ¡£
8.3 ³ÌÐò8.7ÖÐÎÒÃÇÏÈÈø¸½ø³ÌÊä³ö£¬µ«Êǵ±¸¸½ø³ÌÊä³öÍê±Ï×Ó½ø³ÌÒªÊä³öʱ£¬ÎÒ
ÃÇÒªÈø¸½ø³ÌÖÕÖ¹¡£ÊÇ·ñ¸¸½ø³ÌÏÈÖÕÖ¹»òÊÇ×Ó½ø³ÌÏÈÖ´ÐÐÊä³öÒªÒÀÀµÓÚÄں˶ÔÁ½¸ö
½ø³ÌµÄµ÷¶È¡£shellÔÚ¸¸½ø³ÌÖÕÖ¹ºó»á¿ªÊ¼Ö´ÐÐÆäËü³ÌÐò£¬ÕâÑùÒ²ÐíÈÔ»áÓ°Ïì×Ó½ø
³Ì¡£Òª±ÜÃâÕâÖÖÇé¿ö¾ÍÊÇÔÚ×Ó½ø³ÌÍê³ÉÊä³öºó²ÅÖÕÖ¹¸¸½ø³Ì¡£ÓÃÏÂÃæµÄÓï¾äÌæ»»³Ì
ÐòÖÐforkºóÃæµÄ´úÂë¡£ÓÉÓÚÖ»ÓÐÖÕÖ¹¸¸½ø³Ì²ÅÄÜ¿ªÊ¼ÏÂÒ»¸ö³ÌÐò£¬ËùÒÔ²»»á³öÏÖÉÏ
ÃæµÄÇé¿ö¡£
else if ( pid == 0 ) {
WAIT_PARENT( ) ;
/*parent goes first */
charatatime ( "output form child\n" ) ;
TELL_PARENT ( getppid( )) ;
* tell parent we're done */
} else {
charatatime ( "output from parent\n" ) ;
TELL_CHILD ( pid ) ;
* tell child we're done */
WAIT_CHILD ( ) ;
/* wait for child to finish */
8.4 ¶Ôargv[2]´òÓ¡µÄÊÇÏàͬµÄÖµ£¨/home/stevens/bin/testinterp£©¡£ÔÒòÊÇex
eclpÔÚ½áÊøʱµ÷ÓÃÁËexecve£¬²¢ÇÒÓëÖ±½Óµ÷ÓÃexeclµÄ·¾¶ÃûÏàͬ¡£
8.5²»Ìṩ·µ»Ø±£´æµÄÓû§IDµÄº¯Êý£¬ÎÒÃDZØÐëÔÚ½ø³Ì¿ªÊ¼Ê±±£´æÓÐЧµÄÓû§ID¡£
8.6 ³ÌÐòC.7´´½¨ÁËÒ»¸özombie¡£
#include "ourhdr.h"
int
main(void)
{
pid_t pid;
if ( (pid = fork()) < 0)
err_sys("fork error");
else if (pid == 0) /* child */
exit(0);
/* parent */
sleep(4);
system("ps");
exit(0);
}
³ÌÐòC.7 ´´½¨Ò»¸özombie²¢ÓÃps²é¿´Æä״̬
Ö´ÐгÌÐò½á¹ûÈçÏ£¨ps£¨1£©ÓÃ"Z"±íʾZombie£©£º
$ a.out
PID TT STAT TIME COMMAND
5940 p3 S 0:00 a.out
5941 p3 Z 0:00 <defunct> the zombie
5942 p3 S 0:00 sh -c ps
5943 p3 R 0:00 ps
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Á¿£¬ËùÒÔinit½ø³ÌÖªµÀʲôʱºòÖÕ¶ËÓû§×¢Ïú¡£
ÍøÂçloginûÓаüº¬init£¬ÏàÓ¦µÄlogoutÏîÊÇÓÉÒ»¸ö´¦Àílogin²¢¼à²âlogoutµÄ½ø
³ÌдµÄ¡£(±¾ÀýÖÐΪtelnetd)
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10.1 µ±³ÌÐòµÚÒ»´Î½Óµ½ÎÒÃÇ·¢Ë͸øËüµÄÐźÅÁ¿¾ÍÖÕÖ¹ÁË¡£ÒòΪһ²¶×½µ½ÐźÅÁ¿pa
useº¯Êý¾Í·µ»Ø¡£
10.2 ³ÌÐòC.8ʵÏÖÁËraiseº¯Êý¡£
#include <sys/types.h>
#include <signal.h>
#include <unistd.h>
int
raise(int signo)
{
return( kill(getpid(), signo) );
}
³ÌÐòC.8 raiseº¯ÊýµÄʵÏÖ
10.3 ¼ûͼC.3¡£
ͼC.3 longjumpÇ°ºóµÄ¶Ñջ״̬
´Ósig_alrmͨ¹ýlongjmp·µ»Ømain£¬ÓÐЧµØ±ÜÃâÁ˼ÌÐøÖ´ÐÐsig_int¡£
10.4 Èç¹û½ø³ÌÔÚµ÷ÓÃalarmºÍsetjmpÖ®¼ä±»ÄÚºË×èÈûÁË£¬alarmʱ¼ä×ßÍêÖ®ºó¾Íµ÷
ÓÃÐźÅÁ¿´¦Àí³ÌÐò£¬È»ºóµ÷ÓÃlongjmp¡£µ«ÊÇÓÉÓÚûÓе÷ÓÃsetjmp£¬ËùÒÔûÓÐÉèÖÃ
env_alrm»º´æÇø¡£Èç¹ûlongjmpµÄÌøת»º´æÇøûÓб»setjmp³õʼ»¯£¬Ôò˵Ã÷ûÓж¨
ÒålongjmpµÄ²Ù×÷¡£
10.5 ²Î¼û" Implementing Software Timers " by Don Libers ( C user Journa
l, Vol. 8, no. 11, Nov. 1990 )ÖеÄÀý×Ó¡£
10.7 Èç¹û½ö½öµ÷ÓÃ_exit£¬Ôò½ø³ÌÖÕֹ״̬¾Í²»Äܱíʾ¸Ã½ø³ÌÊÇÓÉÓÚSIGABRTÐźÅ
Á¿¶øÖÕÖ¹µÄ¡£
10.8 Èç¹ûÐźÅÁ¿ÊÇÓÉÆäËüÓû§µÄ½ø³Ì·¢³öµÄ£¬½ø³Ì±ØÐëÉèÖÃÓû§µÄIDΪ¸ù»òÕßÊÇ
½ÓÊÕ½ø³ÌµÄÓµÓÐÕߣ¬·ñÔòkill²»ÄÜÖ´ÐС£ËùÒÔʵ¼ÊµÄÓû§IDΪÐźÅÁ¿µÄ½ÓÊÕÕßÌṩ
Á˸ü¶àµÄÐÅÏ¢¡£
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IZE¡£ÀýÈçÏÂÃæµÄ´úÂë¿ÉÒÔʹfd_setÊý¾ÝÀàÐÍ°üº¬2048¸öÃèÊö·û¡£
#define FD_SETSIZE 2048
#include <sys/types.h>
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FD_ZERO sigemptyset
FD_SET sigaddset
FD_CLR sigdelset
FD_ISSET sigismember
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#include <sys/types.h>
#include <sys/time.h>
#include <stddef.h>
#include "ourhdr.h"
void
sleep_us(unsigned int nusecs)
{
struct timeval tval;
tval.tv_sec = nusecs / 1000000;
tval.tv_usec = nusecs % 1000000;
select(0, NULL, NULL, NULL, &tval);
}
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#include <sys/types.h>
#include <poll.h>
#include <stropts.h>
#include "ourhdr.h"
void
sleep_us(unsigned int nusecs)
{
struct pollfd dummy;
int timeout;
if ( (timeout = nusecs / 1000) <= 0)
timeout = 1;
poll(&dummy, 0, timeout);
}
³ÌÐòC.10 ÓÃpollʵÏÖsleep_usº¯Êý
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#include <sys/types.h>
#include <sys/time.h>
#include "ourhdr.h"
int
main(void)
{
int i, n, fd[2];
fd_set writeset;
struct timeval tv;
if (pipe(fd) < 0)
err_sys("pipe error");
FD_ZERO(&writeset);
for (n = 0; ; n++) { /* write 1 byte at a time until pipe is full */
FD_SET(fd[1], &writeset);
tv.tv_sec = tv.tv_usec = 0; /* don't wait at all */
if ( (i = select(fd[1]+1, NULL, &writeset, NULL, &tv)) < 0)
err_sys("select error");
else if (i == 0)
break;
if (write(fd[1], "a", 1) != 1)
err_sys("write error");
}
printf("pipe capacity = %d\n", n);
exit(0);
}
³ÌÐòC.11 ÓÃselect¼ÆËã¹ÜµÀµÄÐÔÄÜ
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#include "ourhdr.h"
int
main(void)
{
char *ptr, buff[MAXLINE];
daemon_init();
close(0);
close(1);
close(2);
ptr = getlogin();
sprintf(buff, "login name: %s\n",
(ptr == NULL) ? "(empty)" : ptr);
write(3, buff, strlen(buff));
exit(0);
}
³ÌÐòC.12 µ÷ÓÃdaemon_init»ñµÃ×¢²áÃû
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¡£
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14.2 ¸¸½ø³ÌÏò¹ÜµÀдÍê×îºóÒ»ÐÐÒÔºó¾ÍÖÕÖ¹ÁË£¬È»ºó¶ÁÕ߶Áµ½¹ÜµÀµÄ½áβʱ×Ô¶¯
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err_sys ( "setvbuf error" ) ;
whileÖеÄreadºÍwriteÓÃÏÂÃæµÄÓï¾ä´úÌæ¡£
if (fputs ( line, fpout ) == EOF )
err_sys ( "fputs error to pipe" ) ;
if ( fgets ( line, MAXLINE, FPIN ) == NULL ) {
err_msg ( "child close pipe" ) ;
break ;
}
14.6 ËäÈ»systemº¯Êýµ÷ÓÃÁËwait£¬µ«ÊÇÖÕÖ¹µÄµÚÒ»¸ö×Ó½ø³ÌÊÇÓÉpopen²úÉúµÄ£¬Ëù
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¶Á¡£µ«ÊÇÒ»µ©¶ÁÍêÁËËùÓеÄÊý¾Ýread¾Í·µ»Ø0£¬¼´±íÃ÷µ½ÁËÎļþβ¡£poll¶ÁÍêÁËËù
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tring°üº¬Öض¨Ïò2 > &1ÃüÁ¾Í¿ÉÒÔ½«±ê×¼³ö´í·¢Ë͸ø¸¸½ø³Ì¡£
14.9 popenÉú³ÉÒ»¸ö×Ó½ø³Ì£¬×Ó½ø³Ìͨ¹ýexecÖ´ÐÐBourne shell¡£È»ºóShellÔÙµ÷
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14.10 ½â¾öµÄ°ì·¨ÊÇ´ò¿ªFIFOÁ½´Î£¬Ò»´Î¶ÁÒ»´Îд¡£Ò»°ãÎÒÃDz»»á¶Ô´ò¿ªµÄÃèÊö·û
½øÐÐд£¬ÎÒÃǾø²»»áʹÓÃΪд¶ø´ò¿ªµÄÃèÊö·û£¬µ«ÊÇʹ¸ÃÃèÊö·û´ò¿ª¾Í¿ÉÔÚ¿Í»§Êý
´Ó1±äΪ0ʱ£¬×èÖ¹²úÉúÎļþÖÕÖ¹¡£´ò¿ªFIFOÁ½´ÎÐèҪעÒâÏÂÁвÙ×÷·½Ê½£ºµÚÒ»´ÎÒÔ
·Ç×èÈû¡¢Ö»¶Á·½Ê½open£¬µÚ¶þ´ÎÒÔ×èÈû¡¢Ö»Ð´·½Ê½open¡£(Èç¹ûÓ÷Ç×èÈû¡¢Ö»Ð´·½
ʽ´ò¿ª½«·µ»Ø´íÎó¡£)È»ºó¹Ø±Õ¶ÁÃèÊö·ûµÄ·Ç×èÈûÊôÐÔ¡£²Î¼û³ÌÐòC.13¡£
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "ourhdr.h"
#define FIFO "temp.fifo"
int
main(void)
{
int fdread, fdwrite;
unlink(FIFO);
if (mkfifo(FIFO, FILE_MODE) < 0)
err_sys("mkfifo error");
if ( (fdread = open(FIFO, O_RDONLY | O_NONBLOCK)) < 0)
err_sys("open error for reading");
if ( (fdwrite = open(FIFO, O_WRONLY)) < 0)
err_sys("open error for writing");
clr_fl(fdread, O_NONBLOCK);
exit(0);
}
³ÌÐòC.13 ÒÔ·Ç×èÈû·½Ê½´ò¿ªFIFO½øÐжÁд²Ù×÷
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