《aix系统应用基础》

ksh
script commands
.
(1) (2) (3)
Subshell
(1) (2) (3)
10
Invoking Shell Scripts (2 of 3)
$ cat hello
echo "Hello, John. Today is: $(date)" pwd ls $ chmod +x hello
.
2
What Is a Process?
Each program runs in a process: The Process Environment
Program
User and group ID
Data Open files Current directory
Process ID (PID) Parent Process ID (PPID) Program variables
.
11
Invoking Shell Scripts (3 of 3)
$ cat set_dir
dir1=/tmp dir2=/usr
$ . set_dir
$ echo $dir1 /tmp $ echo $dir2 /usr
. (dot): Execution in the current shell
$ cat hello
echo "Hello, John. Today is: $(date)" pwd ls
$ ksh hello
Hello, John: Today is: Wed Sep 13 19:34 /home/john books letter1 text2sarah
$_
-ksh $ ksh hello
login:
AIX System PID=202 -ksh
login: john John's Password: xxxxxx
$_
Environment
program uid gid files PID
/usr/bin/ksh john staff /dev/tty1 202
.
4
Process Environment
.
5
Parents and Children
$ echo $$ 202
$ ksh
$ echo $$ 206
(Create a subshell)
Subshell
$ date (Run a command)
Tue Jan 4 11:18:26 GMT 2000
$ <ctrl-d>
(Exit the subshell)
$ echo $$ 202
PID PPID
-ksh
202 1
ksh
206 202
date
208 206
.
6
Variables and Processes
Variables are part of the process environment. Processes cannot access or change variables from another
?
What is the value of dir1 and dir2, if set_dir is called without the dot?
.
12
Exit Codes from Commands
A command returns an exit value to the parent process:
process.
$ x=4 $ ksh $ echo $x
Subshell
$ x=1 $ <ctrl-d> $ echo $x 4
.
7
Activity: Exporting Variables
varl
export variable=value
.
8
What Is a Shell Script?
$ hello
Hello, John: Today is: Wed Sep 13 19:34 /home/john books letter1 text2sarah $_
(1) (2) (3)
Subshell
(1) (2) (3)
The shell uses the PATH variable to find executable programs.
0
=
1 - 255 =
Success Other than successful
The environment variable $? contains the exit value of the last command:
A shell script is a collection of commands stored in a text file
$ vi hello
echo "Hello, John. Today is: $(date)" pwd ls
~ ~ ~ :wq
$
.
9
Invoking Shell Scripts (1 of 3)
$ cat kfile
AIX System
PID=202 -ksh PID=310 cat
Environment during execution
program uid gid files
parent PID PPID
/usr/bin/cat john staff /dev/tty1 kfile -ksh 310 202
Unit 10 Processes
.
Course materials may not be reproduced in whole or in part without the prior written permission of IBM.
5.0
4.1
Unit Objectives
After completing this unit, you should be able to: ● Define an AIX process ● Describe the relationship between parent and child processes ● Create and invoke shell scripts
The variable $$ shows the process ID of the current shell:
$ echo $$ 4712
The ps command shows the running processes:
$ ps -u team01
.
3
Login Process Environment