I have an assignment from school to write a shell program in linux. the idea is to exercise fork() and execv() functions.. the shell program is supposed to be the master and every command that the user prints will run in a new process. we also need to try running the command in every path from the enviroment variable PATH.
for some reason, the execv function isn't working.. any idea what i'm doing wrong?
Yep, that's right.
I'm writing a Linux binary that requires an X11 Server. It will also be released in a Shell, Win32, and Cocoa (Mac OS X).
It's a program that's a text editor and more. It not just creates TXT and RTF files, it also can save in XML, RSS, and a whole lot of other formats.
... (11 Replies)
Hey guys..
I'm trying to learn how to script in bash...
THIS IS NOT AN ASSIGNMENT but my instructor says to learn you must practice
I'm trying to add to a program I'm writing that will print and save raw data...
What syntax commands would I use to write them?
And Thank you... (2 Replies)
Hello. I'm trying to write a shell script that will take files that have .tar, .tar.gz, .tar.Z, .gz, .Z and .zip file extensions and uncompress and unarchive them. The script should be able to take multiple arguments. So far I can write a script using the case command that will do this but it will... (3 Replies)
Can anyone create a program that
would test the math skills of the user. Assume that it would test integer addition, The program should ask the question,collect the integer response, evaluate and notify the user if their answer was correct or incorrect. I would assume integers in the range... (5 Replies)
Hi guys
I'm having trouble with trying to create a script which calculates the grade of a student and the marks out of 300.
The grades are:
0-49% fail
50-59% pass
60-69% credit pass
70-79% distinction
80-100% high distinction
less than 0 or greater than 100 displays error message.
My... (1 Reply)
to determine if two two doubles are equal, we check to see if
their absolute difference is very close to zero. . .if two numbers
are less than .00001 apart, theyre equal.
keep a count field in each record (as you did in p5).
once the list is complete, ask the user to see if an element
is on... (2 Replies)
I want to write a C++ program that uses a class to do some calculations.
I pass arguments to the program, some of which are used to set up class members. A class function will then perform the necessary calculations.
I am wondering how I should pass the arguments from the program to set the... (2 Replies)
1. The problem statement, all variables and given/known data:
Basic Assignment
Write a program similar to the Unix "tee" command.
Program
The Unix "tee" command is used to pull out copies of a data stream. It is typically used in conjunction with pipes (analogous to a T-joint in plumbing, hence... (1 Reply)
Use and complete the template provided. The entire template must be completed. If you don't, your post may be deleted!
1. The problem statement, all variables and given/known data:
Write the a shell script program to remove all space characters stored in the shell variable TEXT.... (7 Replies)
Discussion started by: kofine05
7 Replies
LEARN ABOUT REDHAT
exec
EXEC(3) Linux Programmer's Manual EXEC(3)NAME
execl, execlp, execle, execv, execvp - execute a file
SYNOPSIS
#include <unistd.h>
extern char **environ;
int execl(const char *path, const char *arg, ...);
int execlp(const char *file, const char *arg, ...);
int execle(const char *path, const char *arg , ..., char * const envp[]);
int execv(const char *path, char *const argv[]);
int execvp(const char *file, char *const argv[]);
DESCRIPTION
The exec family of functions replaces the current process image with a new process image. The functions described in this manual page are
front-ends for the function execve(2). (See the manual page for execve for detailed information about the replacement of the current
process.)
The initial argument for these functions is the pathname of a file which is to be executed.
The const char *arg and subsequent ellipses in the execl, execlp, and execle functions can be thought of as arg0, arg1, ..., argn.
Together they describe a list of one or more pointers to null-terminated strings that represent the argument list available to the executed
program. The first argument, by convention, should point to the file name associated with the file being executed. The list of arguments
must be terminated by a NULL pointer.
The execv and execvp functions provide an array of pointers to null-terminated strings that represent the argument list available to the
new program. The first argument, by convention, should point to the file name associated with the file being executed. The array of
pointers must be terminated by a NULL pointer.
The execle function also specifies the environment of the executed process by following the NULL pointer that terminates the list of argu-
ments in the parameter list or the pointer to the argv array with an additional parameter. This additional parameter is an array of point-
ers to null-terminated strings and must be terminated by a NULL pointer. The other functions take the environment for the new process
image from the external variable environ in the current process.
Some of these functions have special semantics.
The functions execlp and execvp will duplicate the actions of the shell in searching for an executable file if the specified file name does
not contain a slash (/) character. The search path is the path specified in the environment by the PATH variable. If this variable isn't
specified, the default path ``:/bin:/usr/bin'' is used. In addition, certain errors are treated specially.
If permission is denied for a file (the attempted execve returned EACCES), these functions will continue searching the rest of the search
path. If no other file is found, however, they will return with the global variable errno set to EACCES.
If the header of a file isn't recognized (the attempted execve returned ENOEXEC), these functions will execute the shell with the path of
the file as its first argument. (If this attempt fails, no further searching is done.)
RETURN VALUE
If any of the exec functions returns, an error will have occurred. The return value is -1, and the global variable errno will be set to
indicate the error.
FILES
/bin/sh
ERRORS
All of these functions may fail and set errno for any of the errors specified for the library function execve(2).
SEE ALSO sh(1), execve(2), fork(2), environ(5), ptrace(2)COMPATIBILITY
On some other systems the default path (used when the environment does not contain the variable PATH) has the current working directory
listed after /bin and /usr/bin, as an anti-Trojan-horse measure. Linux uses here the traditional "current directory first" default path.
The behavior of execlp and execvp when errors occur while attempting to execute the file is historic practice, but has not traditionally
been documented and is not specified by the POSIX standard. BSD (and possibly other systems) do an automatic sleep and retry if ETXTBSY is
encountered. Linux treats it as a hard error and returns immediately.
Traditionally, the functions execlp and execvp ignored all errors except for the ones described above and ENOMEM and E2BIG, upon which they
returned. They now return if any error other than the ones described above occurs.
CONFORMING TO
execl, execv, execle, execlp and execvp conform to IEEE Std1003.1-88 (``POSIX.1'').
BSD MANPAGE 1993-11-29 EXEC(3)