How can 'popen()' be used for reading and writing to opening pipe?
If i try 'popen("prog", "rw")'
and then put and get chars - it does
not work.
What is wrong? (1 Reply)
I am trying to write a script that will do a sql statement. But in the sql I will have a list (1,2,3,4).
How would I go about asking for the input from the user running the script, and then transferring that back into the list as say ($var1,$var2,$var3)?
It would be somewhat like this:
... (1 Reply)
I need to find all the files that have group Read or Write permission or files that have user write permission.
This is what I have so far:
find . -exec ls -l {} \; | awk '/-...rw..w./ {print $1 " " $3 " " $4 " " $9}'
It shows me all files where group read = true, group write = true... (5 Replies)
Hi all,
I have a problem with some read/write functions.
I have a .bin file which contains a lot of structures as follows:
struct alumno
{
char id;
char apellido1;
char apellido2;
char nombre;
float nota1p;
float nota2p;
float notamedia;
char photofilename;
};
What I have... (3 Replies)
Hi,
We have smb client running on two of the linux boxes and smb server on another linux system. During a backup operation which uses smb, read of a file was allowed while write to the same file was going on.Also simultaneous writes to the same file were allowed.Following are the settings in the... (1 Reply)
HI
I need to implement a client/server TCP application. the customer is the client and the bartender is the server.
When the customer enter the Bar, client connects to the server
Server should reply the client immediately. Other wise if the server is busy, it should send an update message... (10 Replies)
EDIT: Nevermind. I found a forth kludge to get around the psed requirement!
Short version: I'm trying to use the "w" flag with psed to write all substituted lines into another file. No matter how many times I read the man pages or search with Google, I can't seem to find the proper syntax... (0 Replies)
Hi Everyone,
newbie here, please help me i can't read the code i'm confused reading this code.
select c.net_svc_id, c.inst_st_dt into ${REO_RECON_USERID_LUZON_TEMP} from ${WO_INST_SITE_COMP_FIELDS} a, ${WO_INST_SITE_COMPONENTS} b, ${WO_INST} c where a.cust_ac_no = b.cust_ac_no and... (3 Replies)
I have got a file in following format:
AAAAAAA
BBBBBBBB
CCCCCCC
DDDDDDD
I am trying to read this file and out put it in following format:
AAAAAAA,BBBBBBB,CCCCCCC,DDDDDD
Preferred method is shell or Perl.
Any help appreciated. (11 Replies)
Can someone help me to write this program in C in QNX?
Using the FIFO queues write a simple communication system consisting of programs write and read. The program write the parameters given strings enclosed in single quotes. These strings are written to the FIFO file. Reads the program read... (1 Reply)
Discussion started by: ebasse2
1 Replies
LEARN ABOUT REDHAT
read
READ(2) Linux Programmer's Manual READ(2)NAME
read - read from a file descriptor
SYNOPSIS
#include <unistd.h>
ssize_t read(int fd, void *buf, size_t count);
DESCRIPTION
read() attempts to read up to count bytes from file descriptor fd into the buffer starting at buf.
If count is zero, read() returns zero and has no other results. If count is greater than SSIZE_MAX, the result is unspecified.
RETURN VALUE
On success, the number of bytes read is returned (zero indicates end of file), and the file position is advanced by this number. It is not
an error if this number is smaller than the number of bytes requested; this may happen for example because fewer bytes are actually avail-
able right now (maybe because we were close to end-of-file, or because we are reading from a pipe, or from a terminal), or because read()
was interrupted by a signal. On error, -1 is returned, and errno is set appropriately. In this case it is left unspecified whether the
file position (if any) changes.
ERRORS
EINTR The call was interrupted by a signal before any data was read.
EAGAIN Non-blocking I/O has been selected using O_NONBLOCK and no data was immediately available for reading.
EIO I/O error. This will happen for example when the process is in a background process group, tries to read from its controlling tty,
and either it is ignoring or blocking SIGTTIN or its process group is orphaned. It may also occur when there is a low-level I/O
error while reading from a disk or tape.
EISDIR fd refers to a directory.
EBADF fd is not a valid file descriptor or is not open for reading.
EINVAL fd is attached to an object which is unsuitable for reading.
EFAULT buf is outside your accessible address space.
Other errors may occur, depending on the object connected to fd. POSIX allows a read that is interrupted after reading some data to return
-1 (with errno set to EINTR) or to return the number of bytes already read.
CONFORMING TO
SVr4, SVID, AT&T, POSIX, X/OPEN, BSD 4.3
RESTRICTIONS
On NFS file systems, reading small amounts of data will only update the time stamp the first time, subsequent calls may not do so. This is
caused by client side attribute caching, because most if not all NFS clients leave atime updates to the server and client side reads satis-
fied from the client's cache will not cause atime updates on the server as there are no server side reads. UNIX semantics can be obtained
by disabling client side attribute caching, but in most situations this will substantially increase server load and decrease performance.
Many filesystems and disks were considered to be fast enough that the implementation of O_NONBLOCK was deemed unneccesary. So, O_NONBLOCK
may not be available on files and/or disks.
SEE ALSO close(2), fcntl(2), ioctl(2), lseek(2), readdir(2), readlink(2), select(2), write(2), fread(3), readv(3)Linux 2.0.32 1997-07-12 READ(2)
05-07-2010
