03-31-2013
Create a program illustrating SUID
To understand SUID feature, I set SUID bit for a SHELL script.
Then I executed the program by a different user.
In order to understand how it works, I tried different ways like:
1) I didn't give execute permission for the other user (not an owner) and then he tried to execute it.
2) I made the script coded in a way so that when the owner runs, it behaves differently than when other user runs. This I did by including $LOGNAME in the script.
I also tried a few other ways to understand SUID but all these couldn't make me get how SUID works.
Please give me a SHELL script or whatever required so that I get how SUID can be used in real time.
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SCRIPT(1) BSD General Commands Manual SCRIPT(1)
NAME
script -- make typescript of terminal session
SYNOPSIS
script [-a] [-c COMMAND] [-f] [-q] [-t] [file]
DESCRIPTION
Script 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.
Options:
-a Append the output to file or typescript, retaining the prior contents.
-c COMMAND
Run the COMMAND rather than an interactive shell. This makes it easy for a script to capture the output of a program that behaves
differently when its stdout is not a tty.
-f Flush output after each write. This is nice for telecooperation: One person does `mkfifo foo; script -f foo' and another can super-
vise real-time what is being done using `cat foo'.
-q Be quiet.
-t Output timing data to standard error. This data contains two fields, separated by a space. The first field indicates how much time
elapsed since the previous output. The second field indicates how many characters were output this time. This information can be used
to replay typescripts with realistic typing and output delays.
The script ends when the forked shell 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. Script works best with commands that do not manipulate
the screen, the results are meant to emulate a hardcopy terminal.
ENVIRONMENT
The following environment variable is utilized by script:
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) (for the history mechanism), scriptreplay(1).
HISTORY
The script command appeared in 3.0BSD.
BUGS
Script places everything in the log file, including linefeeds and backspaces. This is not what the naive user expects.
AVAILABILITY
The script command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
Linux July 30, 2000 Linux