1. Hewlett-Packard Company
5/12/2018
PROGRAMMING AND POSIX
Steve Hoogheem
Hewlett-Packard Company
Everybody got a handout?
Introduce myself.
Who’s new to MPE?
Who’s new to POSIX?

2. Contents Getting Started A Simple Program and a CGI Program
5/12/2018
Contents
Getting Started
A Simple Program and a CGI Program
The Hierarchical File System (HFS)
Files and Directories - A Review
Creating and Linking with Libraries
POSIX Topics
Additional Programming Topics

3. Getting Started Logon: Enter the POSIX shell: Exit the POSIX shell:
5/12/2018
Getting Started
Logon:
:hello <user>.<account>
Enter the POSIX shell:
:sh if HPPXUDC.PUB.SYS UDC set or
:xeq sh.hpbin.sys -L
Exit the POSIX shell:
> exit
POSIX shell vs. MPE CI or Command Interpreter

4. A Simple Program and A CGI Program
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A Simple Program and A CGI Program
A Simple Program
Create the file
Compile and link
Run it
A CGI Program
Test it
Run it from a web browser

5. A Simple Program - 1 Create the source file:
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A Simple Program - 1
Create the source file:
> cat >hw.c Enter/Return to start new line
#include <stdio.h> /* printf() */
main() {
printf("hello world\n"); }
:eod or CTRL-Y to end or
> vi hw.c

6. A Simple Program - 2 Compile and link the source file:
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A Simple Program - 2
Compile and link the source file:
> c89 -o hw -D_POSIX_SOURCE hw.c
Run the program:
> hw
hello world
Use compile directive _POSIX_SOURCE
Alternatively, you can define it in the source itself
Who’s new to c89?

7. A CGI program - 1 Edit the source file: #define _POSIX_SOURCE
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A CGI program - 1
Edit the source file:
> cp hw.c hwcgi.c
> vi hwcgi.c
#define _POSIX_SOURCE
#include <stdio.h>
main() {
printf("Content-type: text/plain\n\n");
printf("hello world\n"); }
Compile and link the program:
> c89 -o hwcgi hwcgi.c

8. A CGI program - 2 Test the CGI program:
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A CGI program - 2
Test the CGI program:
> echo foo | hwcgi | cat
Content-type: text/plain
hello world
Copy CGI program to cgi-bin directory:
> cp hwcgi /APACHE/PUB/cgi-bin
Point browser at:

9. 5/12/2018
A CGI program - 3

10. The Hierarchical File System (HFS)
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The Hierarchical File System (HFS) /
APACHE SYS bin lib usr
PUB PUB NET
cgi-bin htdocs
Absolute path: /APACHE/PUB/cgi-bin/hwcgi
Relative path: ./hwcgi
MPE commands and intrinsics handle HFS files too
Absolute and relative pathnames
MPE escaped syntax - ./file != file used in MPE command
File types: bytestream & fixed record files
- tobyte and frombyte shell commands convert one to the other
POSIX shell vs. MPE Command Interpreter (CI)

11. Working with Files - A Review
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Working with Files - A Review
Naming a file
File Types - bytestream vs. fixed record
Creating and listing files - cat >, vi, ls
Viewing and printing a file - more, cat, lp
Copying, renaming, and removing files - cp, mv, rm
Displaying and changing a file’s permissions and ownership - chmod, chown, chgrp
Naming a file
- can contain up to 256 characters, except when the file is under an MPE group
or account, then 16 characters is the limit
- can be any combination of:
- alphanumeric character
- special character + - _ .
- case matters - file1, FILE1, File1, fILE1 are different files
Creating and listing files
> cat >file Enter/Return to end each line, CTRL-Y to finish
> vi file1
> ls Files starting with . (dot) are hidden and not normally listed, use ls -a
Viewing and printing a file:
> more file1
> cat file1
> lp file1
Copying, renaming, and removing files
> cp file1 file If file2 exists, it is overwritten.
> mv file1 file If file2 exists, it is overwritten.
> rm file2
Displaying and Changing a File’s Permissions and Ownership
Display a file’s permissions:
> ll
-rw-r--r CGI.APACHE APACHE Feb 2 19:26 file1
-rw-r--r CGI.APACHE APACHE Feb 2 19:26 file2
Change a file’s permissions:
> chmod u+x file1
Change a file’s ownership:
> chown MGR.APACHE file1

12. Organizing Files with Directories - A Review
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Organizing Files with Directories - A Review
Displaying your current directory - pwd
Absolute and relative pathnames
Changing to a different directory - cd
Creating a new directory - mkdir
Removing a directory - rmdir

13. Linking with System Libraries
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Linking with System Libraries
Libc is included in link by default
> c89 -o hwcgi hwcgi.c
System libraries located in /lib and /usr/lib
libc, libsvipc are in /lib
libsocket are in /usr/lib
System libraries exist in both archive and shared form (as of MPE 6.0). During link,
archive library (.a suffix) merged into program
shared library (.sl suffix) is NOT merged

14. Linking with Libraries - Syntax
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Linking with Libraries - Syntax
-lfoo means link with library libfoo.a
-lc is included in link by default
-Lpath tells where library is located
-L/lib -L/usr/lib is included in link by default
Link with libsvipc archive library
> c89 -o hwcgi hwcgi.c -lsvipc
Link with libsvipc shared library
> c89 -o hwcgi hwcgi.c -WL,XL=/lib/libsvipc.sl
-WL switch specifies shared library
must specify full pathname

15. Creating an Archive Library - 1
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Creating an Archive Library - 1
Write new helloworld() function:
> cat >helloworld.c
#define _POSIX_SOURCE
#include <stdio.h>
helloworld() {
printf("hello world\n"); }
> c89 -c helloworld.c
Create the archive library:
> ar -rv libhw.a helloworld.o

16. Creating an Archive Library - 2
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Creating an Archive Library - 2
Have our main program:
> cat >hwcgimain.c
#include <stdio.h>
extern void helloworld(void);
main() {
printf("Content-type: text/plain\n\n");
helloworld(); }
> c89 -c -D_POSIX_SOURCE hwcgimain.c
Link the program:
> c89 -o hwcgi hwcgimain.o -L. -lhw
-L switch specifies library location (. is CWD)

17. Creating a Shared Library
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Creating a Shared Library
Create the shared library:
> ld -b -o libhw.sl helloworld.o
Link with the shared library:
> c89 -o hwcgi hwcgimain.o
-WL,cap=ph,XL=/APACHE/CGISRC/libhw.sl
must specify full pathname

18. Programming Review Create files - cat >, vi
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Programming Review
Create files - cat >, vi
Compile C source code - c89
Manage archive libraries - ar
Create shared libraries - ld -b, c89 -b
Link programs - ld, c89
POSIX C compiler - based on 1996 POSIX.1 standard
vs. ISO C - based on 1994 standard

19. POSIX Topics File Sharing Process Management
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POSIX Topics
File Sharing
Process Management
fork
exec
InterProcess Communication
Signals
Sockets
Error handling

20. File Sharing Duplicating file descriptors - dup & dup2
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File Sharing
Duplicating file descriptors - dup & dup2
File management - fcntl
Duplicate an existing file descriptor
Get & set file descriptor flags
Get & set file status flags
Record locking
Supply actual 2nd descriptor with dup2
- If fd2 is open, it is first closed
Fcntl - 4 different functions in 1
1) Duplicate
2) File descriptor flags - only 1 - FD_CLOEXEC - file is closed across an exec
3) File status flags - O_RDONLY, O_WRONLY, O_RDWR, O_APPEND,
O_CREAT, O_TRUNC, O_EXCL, O_NONBLOCK
-set: only O_APPEND and O_NONBLOCK can be changed
4) Record or range locking or byte locking

21. Process Management - fork - 1
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Process Management - fork - 1
pid_t fork(void);
if ( (pid = fork()) < 0)
perror("fork");
else if (pid == 0) /* child */ {
printf(“child: here\n”); }
else /* pid > 0 */ /* parent */
printf(“parent: here\n”);

22. Process Management - fork - 2
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Process Management - fork - 2
Compile & link sample program
> c89 -o forkt forkt.c
Program & user must have PH capability
c89 link adds PH capability by default to program
if -W option is used to add shared library,
must specify cap=ph
>c89 -o … -WL,cap=ph -W,XL=/lib/libsvipc.sl
Run sample program
> forkt
child: here
parent: here
User must have PH capability
: altacct <account> ;cap=+ph done by user with SM capability
:altuser <user>.<account> ;cap=+ph done by AM with AM capability
Like 2 programs in one
More common to start some other program

23. Process Management - exec
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Process Management - exec
6 forms: execl, execve, execvp,
execv, execve, execvp
if ( (pid = fork()) < 0)
perrror("fork");
else if (pid == 0) /* child */ {
if (execl("/bin/echo",
"echo", "child:", "hello", "world", (char *) 0) < 0)
perror("execl");
printf("child: this never prints\n"); }

24. Process Management - execl
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Process Management - execl
Compile & link sample program
> c89 -o execlt execlt.c
Run sample program
> execlt
child: hello world
parent: exiting
Daemons on MPE
- no orphaned processes today
- use MPE batch job for process independent of session
- nohup in Porting Wrappers makes this easy

25. InterProcess Communication (IPC)
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InterProcess Communication (IPC)
Pipes
pipe(fd[2])
FIFOs
mkfifo(pathname)
Message queues
Semaphores
Shared memory
Pipes - unidirectional communication from sender to receiver
- can only be used between related processes
FIFOs - also called named pipes
- unrelated processes can exchange data
Message queues - linked list of messages, identified by a message queue
identifier
Semaphones - a counter used to provide access to a shared data object for
multiple processes
Shared memory - memory region shared by multiple processes
- fastest form of IPC since data is not copied
>>> these 3 function groups found in library /lib/libsvipc.a

26. InterProcess Communication - pipes
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InterProcess Communication - pipes
Pipes easy to demonstrate in shell:
> who am i
ldev TUE 1:04P
> who am I | cut -f1 -d’ ‘
int pipe(int filedes[2]);
Pipes - unidirectional form of communication is the most common

27. Sockets InterProcess communciation across systems via socket address:
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Sockets
InterProcess communciation across systems via socket address:
32-bit IPv4 address
Internet or Unix (local)
Port number
Functions
Server: socket, bind, listen, accept, read
Client: socket, connect, write
Sockets - more commonly called Berkeley Sockets

28. Signals signal() & raise() are ANSI C, not POSIX.1
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Signals
signal() & raise() are ANSI C, not POSIX.1
Use sigaction() instead
Signal is generated, pending, delivered
Signal not delivered if process is executing in system code; signal is delivered upon exit of system code
Process can:
Ignore the signal
Execute a signal-handling function; process resumes where it was interrupted
Restore the default action of the signal
Signal - “a mechanism by which a process may be notified of, or affected by, an event occurring in the system”
Executing system code - if system code is being executed because of, for example, a read, the signal is not delivered until the read completes or errors

29. Error Handling errno is a system global defined in <errno.h>
5/12/2018
Error Handling
errno is a system global defined in <errno.h>
Functions:
char *strerror(int errnum);
void perror(const char *msg);
if ( (fd = open(pathname, O_RDWR)) < 0) {
/* errno already set by open() */
perror("functionX(): open()");
return -1; }

30. Additional Programming Topics
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Additional Programming Topics
Debugging Your Application
Shell Scripts
make utility
Development Tools
GNU Tools
Porting Wrappers

31. Debugging Your Application - 1
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Debugging Your Application - 1
Add printf() statements in your code
use #ifdef DEBUG compile directive
Add perror() statements in your code
use #ifdef PRINT_ERROR compile directive
if ( (fd = open(pathname, O_RDWR)) < 0) {
/* errno already set by open() */
#if defined(DEBUG) || defined(PRINT_ERROR)
sprintf(msg, "functionX(): open(%s, O_RDWR)”, pathname);
perror(msg);
#endif
return -1; }

32. Debugging Your Application - 2
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Debugging Your Application - 2
perror() continued:
if ( functionX(argv[1]) < 0) {
/* errno already set by functionX() */
#if defined(DEBUG) || defined(PRINT_ERROR)
sprintf(msg, "functionY(): functionX(%s)”, argv[1]);
perror(msg);
#endif
return -1; }

33. Debugging Your Application - 3
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Debugging Your Application - 3
MPE System Debugger
> callci “run ./program ;debug”
Symbolic debugger - xdb
use -g switch during compile
> c89 -g ...
link with /SYS/LIB/XDBEND
first, as MANAGER.SYS:
> cd /SYS/LIB; ln -s XDBEND end.o
> c89 -o … /SYS/LIB/end.o
> xdb -h program

34. Shell Scripts Automate steps with a shell script
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Shell Scripts
Automate steps with a shell script
> cat >hwcgi.sh
#!/bin/sh
c89 -c helloworld.c
ar -rv libhw.a helloworld.o
c89 -c hwcgimain.c
c89 -o hwcgi hwcgimain.o -L. -lhw
Execute permission required to execute
> chmod u+x hwcgi.sh
> hwcgi.sh
Special scripts: /etc/profile and .profile
Shell scripts - great way to automate repeating tasks
Once you know shell commands, there’s no scripting language to learn

35. Make utility Rebuilds only components which need rebuilding all: hwcgi
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Make utility
Rebuilds only components which need rebuilding
> cat >Makefile
all: hwcgi
hwcgi: hwcgimain.o libhw.a
$(CC) -o hwcgimain.o -L. -lhw
libhw.a: helloworld.o
$(AR) $(ARFLAGS) $?
> make
make -n to display commands without execution
Make - a great way to automate building your application

36. Development Tools Terminal Emulaters on Windows
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Development Tools
Terminal Emulaters on Windows
Reflection -
Qterm -
Edit files from another system
Samba - http: ://jazz.external.hp.com/src/, select Samba/iX
Development Environments
Whisper Technology -

37. GNU Tools Downloadable software from: Tools include:
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GNU Tools
Downloadable software from:
http: ://jazz.external.hp.com/src/, select GNU
Tools include:
gcc - C compiler
gxx or g++ - C++ compiler
gdb - debugger (port in progress)
gmake - for building software
gzip, gunzip - file compression and decompression
cvs - Concurrent Version System for software control

38. Porting Wrappers Downloadable software from: Additional Functions:
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Porting Wrappers
Downloadable software from:
http: ://jazz.external.hp.com/src/#PortingWrappers
Additional Functions:
Error reporting: pmpeerror, strmpeerror
Mapped regions: mmap, mprotect, msync, munmap
Sockets enabled: fcntl, fstat, stat
Additional Libraries & Header Files
Additional Commands:
ld, nm, nohup
Command wrappers: ftp, ipcs, ipcrm, ping, xdb

39. Error Handling with MPE Intrinsics
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Error Handling with MPE Intrinsics
_mpe_errno, _mpe_intrinsic are system globals defined in <errno.h>
Requires _MPEXL_SOURCE compile directive to use
Porting Wrappers has functions pmpeerror() & strmpeerror() plus header file <mpeerrno.h>
#include <mpeerrno.h>
#pragma intrinsic FCONTROL
FCONTROL(_MPE_FILENO(fildes), 2, &dummy);
if ( ( ccode_return = ccode() ) != CCE ) {
errno = EINVAL;
mpe_errno = ccode_return;
mpe_intrinsic = FCONTROL_INTRINSIC;
#if defined(DEBUG) || defined(PRINT_ERROR)
pmpeerror("functionX(): FCONTROL(2)");
#endif
return -1; }

40. Summary Getting Started A Simple Program and a CGI Program
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Summary
Getting Started
A Simple Program and a CGI Program
The Hierarchical File System (HFS)
Files and Directories - A Review
Creating and Linking with Libraries
POSIX Topics
Additional Programming Topics

41. Additional Resources MPE/iX manuals: Programming with examples:
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Additional Resources
MPE/iX manuals:
HP C/iX Library Reference Manual - function man pages
MPE/iX Developer’s Kit Reference Manual - function man pages
MPE/iX Shell and Utilities User’s Guide - commands, shell, vi, make
New Features of MPE/iX: Using the Hierarchical File System - commands
Programming with examples:
“Advanced Programming in the UNIX Environment” by W. Richard Stevens
- directory util/apue in Porting Wrappers contains Stevens’ main header file and library

42. Additional Resources POSIX make
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Additional Resources
POSIX
“POSIX Programmer's Guide” by Donald Lewine
“The POSIX.1 Standard - A Programmer’s Guide” by Fred Zlotnick
POSIX Specifications from IEEE - very detailed
make
“Managing Projects with make” by Andrew Oram and Steve Talbott
MPE vs. POSIX Functions and Commands