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?
I tried compiling a simple test file just to see if execv works and it did..
it was something like:
Now, am in a very tight situation here. I really dont expect anyone to understand but please, try your best.
am trying to right a program that goes back to the previous entry to correct a mistake.
heres what am trying to do. i write a program like this
Name : James Holgston... (1 Reply)
Hellow every body
I am trying to write a very simple script in an executable file as following
if ($?PWD) then
echo "OK"
else
echo "No"
endif
but I am getting error during execution in c shell as
synthax error at line 4 , unexpected end of file
Please advise (2 Replies)
I am programming the following simple shell program. It works for the most part, things like 'ls' and 'ps' work just fine. However when I add options, (example, ls -l) it does not execute the command. Also, I've been trying to add an "exit" command, so that I don't have to use the iterrupt; but... (3 Replies)
How to write a shell script which takes 3 strings as positional parameters,first and second are file names and third is a directory.if the two files exist in `pwd` and they contain a specific pattern and their size is greater than 32 bytes,moves these files into directory? (1 Reply)
in the beginners book i have it gives an exercise to try. saying to make a script that examines the time. it should keep examining every second or so and say some sort of message. Can anyone help me get going.
Thanks (3 Replies)
I want to print the value of variables a1, a2, a3 in for loop in the following program:
a1=this
a2=is
a3=printed
for((i=1;i<4;i++))
do
var=a$i
#w=`echo $var`
e=${var}
echo $e
done
But actually I get a1,a2,a3 as the output not the "this is printed"
So the main question is if I... (3 Replies)
Iam having file 1 as
wc -l file1 is 8
QWEERTYUU|7927836357398398398913 yuyuyu uyiuyuyuyuy yuiyuiyuyuyy
FDHGFSHAJK|1476887897877777777771 iopwiiwpoi e
.
.
.
.
I Need to read the abouve line in file1
so iam using the command as
tail -n 8... (8 Replies)
Hi all,
I am trying to get a file from an ftp server and i have the list of files which needs to be get from the ftp server.
grep unix_prg*.* log.txt > log1.txt
log1.txt (which has the list of files)
06-29-09 00:00AM 3550258 unix_prg090629
06-28-09 07:00PM ... (7 Replies)
1. I've have to write a shell program that accepts Ctrl+T (in linux os in c language) and should print out the current time and date to the screen. I've written the following code but i've to type ^T individual rather than pressing ctrl+T(^T) to get the output. :
2. How do i make the shell... (2 Replies)
Discussion started by: zorro_phu
2 Replies
LEARN ABOUT REDHAT
execv
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)