12-18-2016
Alright, thank you for clarifying that
---------- Post updated 12-18-16 at 09:20 PM ---------- Previous update was 12-17-16 at 10:28 PM ----------
As I meditated on what you said, I thought of something. In your #3 explanation, would the tty be process "A"? Or would the tty in your example be process "B"? I guess I have a slight and subtle confusion about using "fork" and "forked" in the verb context. When you said "You actually forked a child ("B")", was forking the child a result of calling fork() in process "A", or calling fork() in process "B"? I hope you can see what I'm getting at here. :P
10 More Discussions You Might Find Interesting
1. Shell Programming and Scripting
I'm writing a shell script and I need to replace the contents of a configuration file based on what is passed to the script...can I replace expressions in a file from a bash shell script? (2 Replies)
Discussion started by: HumanBeanDip
2 Replies
2. Shell Programming and Scripting
Hello,
Do you have any idea why the below sed command is also replacing the value of "PARAMETER2" instead of just "PARAMETER" in file1 ?
% parameter=PARAMETER
% new_value=2
% cat file1
PARAMETER=1
PARAMETER2=1
% cat file1 | sed s/*$/${new_value}/1
PARAMETER=2
PARAMETER2=2
Thanks. (3 Replies)
Discussion started by: majormark
3 Replies
3. Shell Programming and Scripting
Hi All,
I have a query on Perl. I have a text file which has 3 lines, i want to only replace the first line with my replaced text and keep the rest of the text. FOr eg
Before change -->
echo:a:pending
echo:b:pending
echo:c:pending
After change --->
echo:a:done
echo:b:pending... (1 Reply)
Discussion started by: tosatesh
1 Replies
4. Shell Programming and Scripting
I'm trying to change the ramfs size in kernel .config automatically.
I have a ramfs_size file generated with du -s
cat ramfs_size
64512
I want to replace the linux .config's ramdisk size with the above value
CONFIG_BLK_DEV_RAM_SIZE=73728
Right now I'm doing something dumb like: ... (3 Replies)
Discussion started by: amoeba
3 Replies
5. Shell Programming and Scripting
Hi,
I have a set of files stored in a single directory that I use to set parameters for a physics code, and I would like to streamline the process of updating them all when I change a parameter. For instance, if the files are called A2000p300ini, A2000p300sub, A2000p300run, and the text in each... (3 Replies)
Discussion started by: BlueChris
3 Replies
6. Shell Programming and Scripting
We have 2 file XML files - FILE1.XML and FILE2.xml - we need copy the contents of FILE1.XML and replace in FILE2.xml pattern "<assignedAttributeList></assignedAttributeList>"
FILE1.XML
1. <itemList>
2. <item type="Manufactured">
3. <resourceCode>431048</resourceCode>
4. ... (0 Replies)
Discussion started by: balrajg
0 Replies
7. Shell Programming and Scripting
I have the following code:
print @testarray;
which returns:
8
8
8
9
How do I return the array like this:
The output is: 8, 8, 8, 9 (5 Replies)
Discussion started by: streetfighter2
5 Replies
8. UNIX for Dummies Questions & Answers
I need to replace all filesnames in a folder as well as its content from AK6 to AK11. Eg Folder has files AK6-Create.xml, AK6-system.py etc.. the files names as well as contents should be changes to AK9-Create.xml, AK9-system.py etc
All files are xml and python scripts.
---------- Post... (0 Replies)
Discussion started by: Candid247
0 Replies
9. UNIX for Dummies Questions & Answers
Hi,
I'm very new to Linux but have been muddling my way through quite happily until recently.
I'm trying to write a program in C++ which starts a new process using the execl command. I am trying to run the tftp process as follows:
char ip_addr = "...";
if (execl("usr/bin/tftp", "tftp",... (2 Replies)
Discussion started by: JoC
2 Replies
10. UNIX for Dummies Questions & Answers
Guys, I have the following code
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>
void read2();
main(int argc, char** argv)
{
int pid,status;
pid=fork();
if ( pid == 0 )
{
read2(argv,... (4 Replies)
Discussion started by: pfpietro
4 Replies
LEARN ABOUT ULTRIX
environ
execl(3) Library Functions Manual execl(3)
Name
execl, execv, execle, execlp, execvp, exect, environ - execute a file
Syntax
execl(name, arg0, arg1, ..., argn, (char *)0)
char *name, *arg0, *arg1, ..., *argn;
execv(name, argv)
char *name, *argv[];
execle(name, arg0, arg1, ..., argn, (char *)0, envp)
char *name, *arg0, *arg1, ..., *argn, *envp[];
execlp(file, arg0, arg1, ..., argn, (char *)0)
char *file, *arg0, *arg1, ..., *argn;
execvp(file,argv)
char *file, *argv[];
exect(name, argv, envp)
char *name, *argv[], *envp[];
extern char **environ;
Description
These routines provide various interfaces to the system call. Refer to for a description of their properties; only brief descriptions are
provided here.
In all their forms, these calls overlay the calling process with the named file, then transfer to the entry point of the core image of the
file. There can be no return from a successful exec. The calling core image is lost.
The name argument is a pointer to the name of the file to be executed. The pointers arg[0], arg[1] ... address null-terminated strings.
Conventionally arg[0] is the name of the file.
Two interfaces are available. is useful when a known file with known arguments is being called; the arguments to are the character strings
constituting the file and the arguments; the first argument is conventionally the same as the file name (or its last component). A 0 argu-
ment must end the argument list.
The version is useful when the number of arguments is unknown in advance. The arguments to are the name of the file to be executed and a
vector of strings containing the arguments. The last argument string must be followed by a 0 pointer.
The version is used when the executed file is to be manipulated with The program is forced to single step a single instruction giving the
parent an opportunity to manipulate its state. On VAX-11 machines, this is done by setting the trace bit in the process status longword.
When a C program is executed, it is called as follows:
main(argc, argv, envp)
int argc;
char **argv, **envp;
where argc is the argument count and argv is an array of character pointers to the arguments themselves. As indicated, argc is convention-
ally at least one and the first member of the array points to a string containing the name of the file.
The argv is directly usable in another because argv[argc] is 0.
The envp is a pointer to an array of strings that constitute the environment of the process. Each string consists of a name, an "=", and a
null-terminated value. The array of pointers is terminated by a null pointer. The shell passes an environment entry for each global shell
variable defined when the program is called. See for some conventionally used names. The C run-time start-off routine places a copy of
envp in the global cell which is used by and to pass the environment to any subprograms executed by the current program.
The and routines are called with the same arguments as and but duplicate the shell's actions in searching for an executable file in a list
of directories. The directory list is obtained from the environment.
Restrictions
If is called to execute a file that turns out to be a shell command file, and if it is impossible to execute the shell, the values of
argv[0] and argv[-1] will be modified before return.
Diagnostics
If the file cannot be found, if it is not executable, if it does not start with a valid magic number if maximum memory is exceeded, or if
the arguments require too much space, a return constitutes the diagnostic; the return value is -1. For further information, see Even for
the super-user, at least one of the execute-permission bits must be set for a file to be executed.
Files
/bin/sh Shell, invoked if command file found by execlp or execvp
See Also
csh(1), execve(2), fork(2), environ(7)
RISC execl(3)