int main ( int argc, char ** argv ) {
   for ( j = 0 ; j < argc ; j ++ )
     printf ( "\targv[%d] : (%s).\n", j, argv [ j ] ) ;

 if ( argc > 1 ) {
     if ( strcmp( argv[1], "?" ) == 0 ) {
          printf ( "Please contact {%s}.\n", Autor ) ;
          exit( 0 ) ;
     } ;
 } ;

 #include <time.h>
 void LeeHora ( char * pszHora )
 {
  time_t MiTiempo ;
     MiTiempo = time ( NULL ) ;
     strftime ( pszHora, 10, "%T", localtime ( & MiTiempo ) ) ;
 } ;

 char szMiTiempo [ 11 ] ;
     LeeHora ( szMiTiempo ) ;

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gcc c compiler

-bash-3.00$ gcc --help Usage: gcc [options] file... Options: -pass-exit-codes Exit with highest error code from a phase --help Display this information --target-help Display target specific command line options (Use '-v --help' to display command line options of sub-processes) -dumpspecs Display all of the built in spec strings -dumpversion Display the version of the compiler -dumpmachine Display the compiler's target processor -print-search-dirs Display the directories in the compiler's search path -print-libgcc-file-name Display the name of the compiler's companion library -print-file-name=<lib> Display the full path to library -print-prog-name=<prog> Display the full path to compiler component -print-multi-directory Display the root directory for versions of libgcc -print-multi-lib Display the mapping between command line options and multiple library search directories -print-multi-os-directory Display the relative path to OS libraries -Wa,<options> Pass comma-separated on to the assembler -Wp,<options> Pass comma-separated on to the preprocessor -Wl,<options> Pass comma-separated on to the linker -Xassembler <arg> Pass on to the assembler -Xpreprocessor <arg> Pass on to the preprocessor -Xlinker <arg> Pass on to the linker -save-temps Do not delete intermediate files -pipe Use pipes rather than intermediate files -time Time the execution of each subprocess -specs=<file> Override built-in specs with the contents of -std=<standard> Assume that the input sources are for -B <directory> Add to the compiler's search paths -b <machine> Run gcc for target , if installed -V <version> Run gcc version number , if installed -v Display the programs invoked by the compiler -### Like -v but options quoted and commands not executed -E Preprocess only; do not compile, assemble or link -S Compile only; do not assemble or link -c Compile and assemble, but do not link -o <file> Place the output into -x <language> Specify the language of the following input files Permissible languages include: c c++ assembler none 'none' means revert to the default behavior of guessing the language based on the file's extension Options starting with -g, -f, -m, -O, -W, or --param are automatically passed on to the various sub-processes invoked by gcc. In order to pass other options on to these processes the -W options must be used.

-lxxx means to link a library named libxxx, so with gcc -lpthread -lrt -lc project1.c -o out you're telling it to link libpthread, librt and libc.

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How to init misc vars

#define bzero( thing, sz ) memset( thing, 0, sz ) bzero( pkt.padding, 18 ) ; memset ( & Ncb, 0, sizeof( Ncb ) ) ; bzero( & Ncb, sizeof( Ncb ) ) ; char my_buffer [ 48 ] ; my_buffer [ 0 ] = '\0' ; char mine_buffer[ BUF_LEN ] ; memset( mine_buffer, '\0', BUF_LEN ) ; char QMgrName [ MQ_Q_MGR_NAME_LENGTH + 1 ] = "" ; QMgrName [ 0 ] = 0 ;

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While loop

unsigned int cnt = 5 ; unsigned long factorial = 1 ; do { factorial *= cnt-- ; /* Multiply, then decrement */ } while ( cnt > 0 ) ; printf ( "{%lu}.\n", factorial ) ;

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send an ARP packet (linux style)

See send_arp.c :

... pending to compile & run on Linux ...

Signals

1) SIGHUP 2) SIGINT (a) 3) SIGQUIT 4) SIGILL   5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE   9) SIGKILL (-) 10) SIGUSR1 11) SIGSEGV 12) SIGUSR2   13) SIGPIPE 14) SIGALRM 15) SIGTERM 17) SIGCHLD   18) SIGCONT 19) SIGSTOP (-) 20) SIGTSTP 21) SIGTTIN   22) SIGTTOU 23) SIGURG 24) SIGXCPU 25) SIGXFSZ   26) SIGVTALRM 27) SIGPROF 28) SIGWINCH 29) SIGIO   30) SIGPWR 31) SIGSYS

Linux supports nearly every signal provided by SVR4, BDS and POSIX, with few exceptions ("The Linux Programmer's Guide", Sven Goldt, v 0.4, March 1995) :

• SIGEMT is not supported.
• SIGINFO is not supported.
• SIGSYS (31) is not supported.
• SIGABRT (6) and SIGIOT are identical.
• SIGIO (29), SIGPOLL and SIGURG (23) are identical.
• SIGBUS (7) is defined as SIGUNUSED.

• 1 SIGHUP - Hangup (POSIX).
• 2 SIGINT - Interrupt (ANSI). Control-C from keyboard.
• 3 SIGQUIT - Quit (POSIX).
• 4 SIGILL - Illegal instruction (ANSI).
• 5 SIGTRAP - Trace trap (POSIX).
• 6 SIGABRT - Abort (ANSI).
• 6 SIGIOT - IOT trap (4.2 BSD).
• 7 SIGBUS - BUS error (4.2 BSD).
• 8 SIGFPE - Floating-point exception (ANSI).
• 9 SIGKILL - Kill, unblockable (POSIX).
• 10 SIGUSR1 - User-defined signal 1 (POSIX).
• 11 SIGSEGV - Segmentation violation (ANSI).
• 12 SIGUSR2 - User-defined signal 2 (POSIX).
• 13 SIGPIPE - Broken pipe (POSIX).
• 14 SIGALRM - Alarm clock (POSIX).
• 15 SIGTERM - Termination (ANSI).
• 16 SIGSTKFLT - Stack fault.
• SIGCLD = SIGCHLD - Same as SIGCHLD (System V).
• 17 SIGCHLD - Child status has changed (POSIX).
• 18 SIGCONT - Continue (POSIX).
• 19 SIGSTOP - Stop, unblockable (POSIX).
• 20 SIGTSTP - Keyboard stop (POSIX).
• 21 SIGTTIN - Background read from tty (POSIX).
• 22 SIGTTOU - Background write to tty (POSIX).
• 23 SIGURG - Urgent condition on socket (4.2 BSD).
• 24 SIGXCPU - CPU limit exceeded (4.2 BSD).
• 25 SIGXFSZ - File size limit exceeded (4.2 BSD).
• 26 SIGVTALRM - Virtual alarm clock (4.2 BSD).
• 27 SIGPROF - Profiling alarm clock (4.2 BSD).
• 28 SIGWINCH - Window size change (4.3 BSD, Sun).
• SIGPOLL = SIGIO - Pollable event occurred (System V).
• 29 SIGIO - I/O now possible (4.2 BSD).
• 30 SIGPWR - Power failure restart (System V).
• 31 SIGSYS - Bad system call.

Lliçons que hem après

• always send integers in Network order.
  Using htonl(), portability to other hosts (as S/390) is allowed.

• you can send 2 messages, but TCP can receive them both in one message
  See man 2 socket on SuSE 7.2 : "Sockets of type SOCK_STREAM are full-duplex streams, similar to pipes. They do not preserve record boundaries."

• timeouts of less than a second

• how to pass a 2-dimension array as parameter

6.2 errors I've found

• a thread blocked on a recv call is awakened with EINTR code (RH 6.2)
  Solution : SuSE 7.2

•  

Pending items

• what's the difference between

     echo $SHELL
    and
     echo ${SHELL}
  

•  

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Links

• url : Static, Shared Dynamic and Loadable Linux Libraries.

• Rexx generated HTML year and month calendar(s).

• Search in Linux Journal

• C file input/output wiki.

• C "while" loop wiki, and "do while" loop wiki.

• Off-by-One error : wiki: use strlcat and strlcpy instead of strncat or strncpy.

• C programming tutorial ; nice WikiBook.

• Common C programming errors

• Advanced Linux programming - get PDFs

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Actualitzat el 20130114 (a).