but he went on the give me an example of using execl using a built-in command(date) when I specifically said in the OP that I already have been given an example of using execl with a command ("The only example done in class by the professor was calling the ps command which is a command and not a script.")
It seems to be clearer now where your problem was: between what you called "built-in" programs (I'd call it "system provided executables" and other executable programs there is absolutely no difference. You can (and you found that out yourself already) treat a shell script the same way you treat any other executable, binary or not.
The only difference is that binaries are directly exectuable: they consist of code natively executable on the processor, so once they get loaded they can be executed by it. In contrast scripts are input files for a certain binary - the shells binary, to be precise.
When you execute a shell script the OS will determine its filetype (there is a set of rules laid down in "/etc/magic") and if it comes to the conclusion it is a shell script it will load its default shell and feed it the script as input. If you want to override this and execute it with a different shell (or any other different binary or because your "/etc/magic" lacks the rule to identify what filetype your script is) you can use a "shebang" to specify the commando processor to feed the script to:
will first load this binary and the feed it the scripts text as input. Because for the script language "#!" is still a comment it won't bother the shell at all.
By the way, perderabo has written a whole article about shebangs in the Frequently-Asked-Questions board: The Shebang explained
I hope this helps
bakunin
These 2 Users Gave Thanks to bakunin For This Post:
Hi,
Ho do I differentiate system call from library call?
for example if I am using chmod , how do I find out if it is a system call or library call?
Thanks
Muru (2 Replies)
Hi,
I am calling a program that greps and returns 72536 bytes of data on STDOUT, say about 7000 lines of data on STDOUT.
I use pipe from the program am calling the above program. Naturally, I execute the above program (through execl() ) throught the child process and try to read the... (4 Replies)
Hi,
I would like to know how to call a program "cmp_size" ... where to put in progam to run it
ex: program checkdisk is below, and it will call a nother problem "cmp_size"
Do I just put the cmp_size program at the end of this program.
Thank you very much,
# check all directory for size... (3 Replies)
Dear all,
Currently I'm working on a C program (OS = ubuntu 9.0.4)in which a USB key will
be mounted and umounted for several times. I read the man page
of the mount system call.
I use the following test code
#include <sys/mount.h>
int main(int argc, char *argv)
{
if... (5 Replies)
I need to write a c program that uses the fork and excel system calls to run the shell script mode invoked like this: "./mode 644 ls -l" (that is the argumetns will always be 644 ls -l)
here's the mode script:
#!/bin/sh
octal="$1"
shift
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... (3 Replies)
Hello everyone!
I'm quite new here, but this forum helped me a lot before without registering :-)
I'll go directly to my problem, I have been searching a bit about this issue but I was not successful.
I need to write a program in C code to notificate me (to my email) when some action is done... (7 Replies)
Write a program using select, which will create some number of child processes that continuously send text messages to the parent process using pipes. Each child has its own pipe that it uses to communicate with the parent. The parent uses select () to decide what pipes should be processed to... (1 Reply)
main()
{
printf("before execl");
execl("/home/nirmala/os/fact","fact");
printf("this line will not be printed");
}
for the above program ,the obj file of fact.c is getting loaded correctly.am getting the output as...
factorial =6
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I would need to call the program 'ethtool' in my C++ program, does anyone know how to do that (if its even possible)? (1 Reply)
Discussion started by: Freaky123
1 Replies
LEARN ABOUT X11R4
exit
exit(1) User Commands exit(1)NAME
exit, return, goto - shell built-in functions to enable the execution of the shell to advance beyond its sequence of steps
SYNOPSIS
sh
exit [n]
return [n]
csh
exit [ ( expr )]
goto label
ksh
*exit [n]
*return [n]
DESCRIPTION
sh
exit will cause the calling shell or shell script to exit with the exit status specified by n. If n is omitted the exit status is that of
the last command executed (an EOF will also cause the shell to exit.)
return causes a function to exit with the return value specified by n. If n is omitted, the return status is that of the last command exe-
cuted.
csh
exit will cause the calling shell or shell script to exit, either with the value of the status variable or with the value specified by the
expression expr.
The goto built-in uses a specified label as a search string amongst commands. The shell rewinds its input as much as possible and searches
for a line of the form label: possibly preceded by space or tab characters. Execution continues after the indicated line. It is an error to
jump to a label that occurs between a while or for built-in command and its corresponding end.
ksh
exit will cause the calling shell or shell script to exit with the exit status specified by n. The value will be the least significant 8
bits of the specified status. If n is omitted then the exit status is that of the last command executed. When exit occurs when executing
a trap, the last command refers to the command that executed before the trap was invoked. An end-of-file will also cause the shell to exit
except for a shell which has the ignoreeof option (See set below) turned on.
return causes a shell function or '.' script to return to the invoking script with the return status specified by n. The value will be the
least significant 8 bits of the specified status. If n is omitted then the return status is that of the last command executed. If return
is invoked while not in a function or a '.' script, then it is the same as an exit.
On this man page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways:
1. Variable assignment lists preceding the command remain in effect when the command completes.
2. I/O redirections are processed after variable assignments.
3. Errors cause a script that contains them to abort.
4. Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a vari-
able 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 TYPE | ATTRIBUTE VALUE |
|Availability |SUNWcsu |
+-----------------------------+-----------------------------+
SEE ALSO break(1), csh(1), ksh(1), sh(1), attributes(5)SunOS 5.10 15 Apr 1994 exit(1)