10-01-2003
Reza.
How much do you know about shell scripting? Those are basic questions. You may do well to do some reading on Bourne, Korn and C shells in Unix. A simple search on the Internet should turn up some useful pages. Use keywords like "Bourne" "Korn" "C Shell" "Unix" "Scripting" or "Tutorial".
1. In Bourne and Korn shell you can define a variable at any time by assigning a value to it:
MYVAR=some_value
Note there are no spaces around the '=' sign and the variable name is upper case by convention.
You may return the value of a variable by preceding the name with a dollar sign:
echo $MYVAR
A script may also receive parameters from the command line in variables $1, $2 ... $9.
e.g
echo $5
would return the 5th command line argument.
So:
MY_FILE=/tmp/output.txt
cat /dev/null > $MY_FILE
or ...
cp $3 $MYFILE.old
Ok. Theres a start with shell script variables. Find out what more you can do with them.
2. To obtain a value from the user use the 'read' command. This command is built into the shell and should always be availalbe to you:
read MY_FILE
The user must enter their value followed by a carriage return, before the value is committed to the variable.
You may then access the value in the variable as before:
echo $MY_FILE
I have given you a very brief and limited overview of Bourne/Korn shell variables, but I really do recommend that you do some futher reading on this topic.
Hope this helps.
MBB
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LEARN ABOUT MOJAVE
script
SCRIPT(1) BSD General Commands Manual SCRIPT(1)
NAME
script -- make typescript of terminal session
SYNOPSIS
script [-adkpqr] [-F pipe] [-t time] [file [command ...]]
DESCRIPTION
The script utility makes a typescript of everything printed on your terminal. It is useful for students who need a hardcopy record of an
interactive session as proof of an assignment, as the typescript file can be printed out later with lpr(1).
If the argument file is given, script saves all dialogue in file. If no file name is given, the typescript is saved in the file typescript.
If the argument command is given, script will run the specified command with an optional argument vector instead of an interactive shell.
The following options are available:
-a Append the output to file or typescript, retaining the prior contents.
-d When playing back a session with the -p flag, do not sleep between records when playing back a timestamped session.
-F pipe
Immediately flush output after each write. This will allow a user to create a named pipe using mkfifo(1) and another user may watch
the live session using a utility like cat(1).
-k Log keys sent to the program as well as output.
-p Play back a session recorded with the -r flag in real time.
-q Run in quiet mode, omit the start, stop and command status messages.
-r Record a session with input, output, and timestamping.
-t time
Specify the interval at which the script output file will be flushed to disk, in seconds. A value of 0 causes script to flush after
every character I/O event. The default interval is 30 seconds.
The script ends when the forked shell (or command) exits (a control-D to exit the Bourne shell (sh(1)), and exit, logout or control-D (if
ignoreeof is not set) for the C-shell, csh(1)).
Certain interactive commands, such as vi(1), create garbage in the typescript file. The script utility works best with commands that do not
manipulate the screen. The results are meant to emulate a hardcopy terminal, not an addressable one.
ENVIRONMENT
The following environment variables are utilized by script:
SCRIPT
The SCRIPT environment variable is added to the sub-shell. If SCRIPT already existed in the users environment, its value is overwrit-
ten within the sub-shell. The value of SCRIPT is the name of the typescript file.
SHELL If the variable SHELL exists, the shell forked by script will be that shell. If SHELL is not set, the Bourne shell is assumed. (Most
shells set this variable automatically).
SEE ALSO
csh(1)
HISTORY
The script command appeared in 3.0BSD.
The -d, -p and -r options first appeared in NetBSD 2.0 and were ported to FreeBSD 9.2.
BUGS
The script utility places everything in the log file, including linefeeds and backspaces. This is not what the naive user expects.
It is not possible to specify a command without also naming the script file because of argument parsing compatibility issues.
When running in -k mode, echo cancelling is far from ideal. The slave terminal mode is checked for ECHO mode to check when to avoid manual
echo logging. This does not work when the terminal is in a raw mode where the program being run is doing manual echo.
If script reads zero bytes from the terminal, it switches to a mode when it only attempts to read once a second until there is data to read.
This prevents script from spinning on zero-byte reads, but might cause a 1-second delay in processing of user input.
BSD
December 4, 2013 BSD