Smith
September 1, 2009, 11:48am
1
Hello
I really wonder what's trap in etc/profile and in each user .profile.
I try to google for it but I think I have no luck. Mostly hit is SNMP traps which I think it is not the same thing.
I want to know ...
What's a "trap 2 3" means and are there any other value I can set please?
Do we still need this value nowaday?
How to enhance this value for more secure?
Please help me T_T
Regards,
seg
September 1, 2009, 12:01pm
2
`man trap`
Basically trap will prevent the /etc/profile script from being canceled or killed.
Smith
September 1, 2009, 2:10pm
3
NAME
trap, onintr - shell built-in functions to respond to (hardware) signals SYNOPSIS
sh
trap [ argument n [ n2 . . . ]] csh
onintr [ -| label] ksh
. trap [ arg sig [ sig2 . . . ]] DESCRIPTION
sh
The trap command argument is to be read and executed when the shell receives numeric or symbolic signal(s) (n). (Note: argument is scanned once when the trap is set and once when the trap is taken.) Trap commands are executed in order of signal number or corresponding symbolic names. Any attempt to set a trap on a signal that was ignored on entry to the current shell is ineffective. An attempt to trap on signal 11 (memory fault) produces an error. If argument is absent all trap(s) n are reset to their original values. If argument is the null string this signal is ignored by the shell and by the commands it invokes. If n is 0 the command argument is executed on exit from the shell. The trap command with no arguments prints a list of commands associated with each signal number. csh
onintr controls the action of the shell on interrupts. With no arguments, onintr restores the default action of the shell on interrupts. (The shell terminates shell scripts and returns to the terminal command input level). With the - argument, the shell ignores all interrupts. With a label argument, the shell executes a goto label when an interrupt is received or a child process terminates because it was interrupted. ksh
trap uses arg as a command to be read and executed when the shell receives signal(s) sig. (Note that arg is scanned once when the trap is set and once when the trap is taken.) Each sig can be given as a number or as the name of the signal. trap commands are executed in order of signal number. Any attempt to set a trap on a signal that was ignored on entry to the current shell is ineffective. If arg is omitted or is -, then the trap(s) for each sig are reset to their original values. If arg is the null (the empty string, e.g., "" ) string then this signal is ignored by the shell and by the commands it invokes. If sig is ERR then arg will be executed whenever a command has a non-zero exit status. If sig is DEBUG then arg will be executed after each command. If sig is 0 or EXIT for a trap set outside any function then the command arg is executed on exit from the shell. The trap command with no arguments prints a list of commands associated with each signal number. On this man page, ksh(1) commands that are preceded by one or two . (daggers) are treated specially in the following ways:
Variable assignment lists preceding the command remain in effect when the command completes.
I/O redirections are processed after variable assignments.
Errors cause a script that contains them to abort.
Words, following a command preceded by .. that are in the format of a variable assignment, are expanded with the same rules as a variable assignment. This means that tilde substitution is performed after the = sign and word splitting and file name generation are not performed.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes: ATTRIBUTE TYPEATTRIBUTE VALUE AvailabilitySUNWcsu SEE ALSO
csh(1) , exit(1) , ksh(1) , sh(1) , attributes(5
Yes. I do man but I do not understand T_T. Do we still use trap to prevent user break from profile script nowaday?
Yes you still have to use trap to prevent a user from breaking out of a shell or killing a shell you don't want them to kill.
Here is a simple list of signals
#define SIGHUP 1
#define SIGINT 2
#define SIGQUIT 3
#define SIGILL 4
#define SIGTRAP 5
#define SIGABRT 6
#define SIGIOT 6
#define SIGUNUSED 7
#define SIGFPE 8
#define SIGKILL 9
#define SIGUSR1 10
#define SIGSEGV 11
#define SIGUSR2 12
#define SIGPIPE 13
#define SIGALRM 14
#define SIGTERM 15
#define SIGSTKFLT 16
#define SIGCHLD 17
#define SIGCONT 18
#define SIGSTOP 19
#define SIGTSTP 20
#define SIGTTIN 21
#define SIGTTOU 22
Smith
September 1, 2009, 8:58pm
5
Thank you very much, BubbaJoe.
I search more and found some link
InformIT: Solaris 10 System Administration Exam Prep: Managing System Processes > Using Signals Safari Books Online - 0789729229 - Solaris? 9 Training Guide (CX-310-014 & CX-310-015): System Administrator Certification
Table 5.12. Signals Available Under Solaris
Signal Number Description
SIGHUP 1 Hangup. Usually means that the controlling terminal has been disconnected.
SIGINT 2 Interrupt. The user can generate this signal by pressing Ctrl+C or Delete.
SIGQUIT 3 Quits the process and produces a core dump.
As far as I understand, TRAP 1 means that it will detect the signal that I was disconnected from the system by hangup the modem (I think because the dial-up or ADSL connection is lost).
Why do we want to use TRAP 1?? If any user was disconnected because hang up then that user can't access the server isn't it?
Anybody could tell me which value I should set for TRAP in etc/profile and /.profile of each user please?