03-15-2011
sorta unrelated question:
if u have an array that not all elements have been put in, and u do a for loop for it, will it crash if it tries to access one of the elements that doesnt have anything in it? If not, is the value equal to NULL ?
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
Howdie everyone...
I have a shell script RemoveFiles.sh
Inside this file, it only has two commands as below:
rm -f ../../reportToday/temp/*
rm -f ../../report/*
My problem is that when i execute this script, nothing happened. Files remained unremoved. I don't see any error message as it... (2 Replies)
Discussion started by: cheongww
2 Replies
2. UNIX for Advanced & Expert Users
Hi all,
In my application i am trying to select some text & then give it to print. for this i am opening a stream using popen & then later closing using pclose.
Now this is working fine in my environment (solaris) but the pclose function is failing at my clients m/c. Even though print is... (3 Replies)
Discussion started by: nimishm123
3 Replies
3. UNIX for Dummies Questions & Answers
whoami | grep < $1 | echo $1
trying to write a script that finds out who the user is and then takes occurences of that username from a file that is passed as an argument and then displays it (6 Replies)
Discussion started by: iago
6 Replies
4. Linux
Can anyone explain how Graphic LCD (CSTN / STN) work in Unix...
From Graphic file thro driver code to display....?
Thanks (1 Reply)
Discussion started by: nat123
1 Replies
5. Linux
********nothing too see here!!!****** (2 Replies)
Discussion started by: TonyChapman
2 Replies
6. Shell Programming and Scripting
Hi falks,
I need to dispaly a list of only directories .
As it written in the manual ,the command to do it is 'ls -d'.
When i issue 'ls -d' i'm getting:
tornado.orca.ent:DB10g :/home/oracle/Create_Database > ls -d
.
Is anyone have any idea why id does not display directories ,or maybe... (11 Replies)
Discussion started by: nir_s
11 Replies
7. UNIX for Advanced & Expert Users
Hi
I am trying to use popen function with wrtie option to give inputs to ftp command.
#include "stdio.h"
int main(int argv ,char *argc)
{
int size=0;
char *buf;
FILE *fp;
fp = popen("ftp","w");
while(getline(&buf,&size,stdin) != -1)
write(fp,buf);... (0 Replies)
Discussion started by: kumaran_5555
0 Replies
8. IP Networking
I have a client machine that was built and loaded with SCO UNIX 2.1.3, (yes it is old). The machine worked fine on the closed network that I tested on in my shop. I then had to change it to the network that it would be connected to. Below is the host file, router and subnet mask file that I usually... (0 Replies)
Discussion started by: NC user
0 Replies
9. Shell Programming and Scripting
My script work on Linux but not work in sun os.
my script.
logFiles="sentLog1.log sentLog2.log"
intial_time="0 0"
logLocation="/usr/local/tomcat/logs/"
sleepTime=600
failMessage=":: $(tput bold)Log not update$(tput rmso) = "
successMessage="OK"
arr=($logFiles)... (7 Replies)
Discussion started by: ooilinlove
7 Replies
10. IP Networking
hi all. and sorry for the random question, but this sparkled a raging flame-war at work and i want more points of view
situation
a router, with linux of some sort,
dhcp client requesting for ip in wan1 (as usual with wan ports)
dhcp server listening in lan1, and assigning ip (as usual... (9 Replies)
Discussion started by: broli
9 Replies
POPEN(3) BSD Library Functions Manual POPEN(3)
NAME
popen, pclose -- process I/O
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <stdio.h>
FILE *
popen(const char *command, const char *type);
int
pclose(FILE *stream);
DESCRIPTION
The popen() function ``opens'' a process by creating an IPC connection, forking, and invoking the shell. Historically, popen was implemented
with a unidirectional pipe; hence many implementations of popen only allow the type argument to specify reading or writing, not both. Since
popen is now implemented using sockets, the type may request a bidirectional data flow. The type argument is a pointer to a null-terminated
string which must be 'r' for reading, 'w' for writing, or 'r+' for reading and writing. In addition if the character 'e' is present in the
type string, the file descriptor used internally is set to be closed on exec(3).
The command argument is a pointer to a null-terminated string containing a shell command line. This command is passed to /bin/sh using the
-c flag; interpretation, if any, is performed by the shell.
The return value from popen() is a normal standard I/O stream in all respects save that it must be closed with pclose() rather than fclose().
Writing to such a stream writes to the standard input of the command; the command's standard output is the same as that of the process that
called popen(), unless this is altered by the command itself. Conversely, reading from a ``popened'' stream reads the command's standard
output, and the command's standard input is the same as that of the process that called popen().
Note that output popen() streams are fully buffered by default.
The pclose() function waits for the associated process to terminate and returns the exit status of the command as returned by wait4().
RETURN VALUES
The popen() function returns NULL if the fork(2), pipe(2), or socketpair(2) calls fail, or if it cannot allocate memory.
The pclose() function returns -1 if stream is not associated with a ``popened'' command, if stream has already been ``pclosed'', or if
wait4(2) returns an error.
ERRORS
The popen() function does not reliably set errno.
SEE ALSO
sh(1), fork(2), pipe(2), socketpair(2), wait4(2), fclose(3), fflush(3), fopen(3), shquote(3), stdio(3), system(3)
STANDARDS
The popen() and pclose() functions conform to IEEE Std 1003.2-1992 (``POSIX.2'').
HISTORY
A popen() and a pclose() function appeared in Version 7 AT&T UNIX.
BUGS
Since the standard input of a command opened for reading shares its seek offset with the process that called popen(), if the original process
has done a buffered read, the command's input position may not be as expected. Similarly, the output from a command opened for writing may
become intermingled with that of the original process. The latter can be avoided by calling fflush(3) before popen().
Failure to execute the shell is indistinguishable from the shell's failure to execute command, or an immediate exit of the command. The only
hint is an exit status of 127.
The popen() argument always calls sh(1), never calls csh(1).
BSD
June 24, 2011 BSD