I know how to read and write if i have a forked process with only one child. However what is involved with reading and writing with many forked processes. Say one parent that forks 5 children, and needs to communicate with all 5 in half duplex.
int temp, counter=0;
do{
pipe(temp);
... (5 Replies)
OK... I'm fairly new to unix having the admin handed to me on a platter w/almost no training.
However, being a programmer, I do pick up things fairly easily, but this one is getting the best of me.
I have a unix server that runs multiple versions of the same ERP system, hand crafted for our... (1 Reply)
Morning All,
Quite a simple one this, I hope. What I want to do is to re-write the first line of a file before it's sent to print. The line will be blank initially, and I want to insert some text. The operation can either be done on the file itself (modifying the file on disk), OR in a... (2 Replies)
I want to try the unix pipe, the command is like this:
echo new | find .
the standard output of the echo should be "new", then I guess find command will use this output as input to find the file named "new". But the output is all the file names in my current dir, the last line is "echo: write... (5 Replies)
Hi -- I'm looking to write to a file after piping output from tail -f through to grep:
#write to a file for all lines with "searchtext" within in error_log:
Expand|Select|Wrap|Line Numbers
tail -f /var/error_log | grep searchtext > output.txt
The above command... (2 Replies)
The "write failed: Broken pipe" message is reported by the file sending PC which run my writed network device driver while 500MB or 900MB is sended!
What does the message mean? Does this mean there is a bug in my driver?
li,kunlun (11 Replies)
Hi friends,
I have a file where I should search for a string and get the rest of the line but without the delimiter using awk.
for example I have the series of string in a file:
input_string.txt
bbb
ccc
aaa
and the mapping file looks like this.
mapping.txt
aaa|12
bbb|23
ccc|43... (11 Replies)
Sed command to replace a line in a file using line number from the output of a pipe.
Is it possible to replace a whole line piped from someother command into a file at paritcular line...
here is some basic execution flow..
the line number is 412
lineNo=412
Now i have a line... (1 Reply)
I am trying to keep variables in a file.
if I have all variables at the same time, I can write them all like below.
echo $var1","$var2","$var3
But, these variables are being calculated at different times then they are lost
so I want to keep them in a file seperated by "," .
echo... (5 Replies)
I have a file as below
Emp1|FirstName|MiddleName|LastName|Address|Pincode|PhoneNumber
1234|FirstName1|MiddleName2|LastName3| Add1 || ADD2|123|000000000
2345|FirstName2|MiddleName3|LastName4|
Add1 || ADD2|
234|000000000
OUTPUT :
... (1 Reply)
Discussion started by: styris
1 Replies
LEARN ABOUT HPUX
popen
popen(3S)popen(3S)NAME
popen(), pclose() - initiate pipe I/O to/from a process
SYNOPSIS DESCRIPTION
creates a pipe between the calling program and a command to be executed by the POSIX shell, (see sh-posix(1)).
The arguments to are pointers to null-terminated strings containing, respectively, a shell command line and an I/O mode, either for reading
or for writing.
returns a stream pointer such that one can write to the standard input of the command if the I/O mode is by writing to the file stream; and
one can read from the standard output of the command if the I/O mode is by reading from the file stream.
Because open files are shared, a type command can be used as an input filter and a type command as an output filter. If mode is other than
or the result is undefined.
A stream opened by should be closed by which waits for the associated process to terminate and returns the exit status of the command.
However, if a call caused the termination status to be unavailable to then returns -1 with errno set to This can happen in one of the fol-
lowing conditions:
o If the signal handler for is set to
o If the signal handler or another thread in the same process issues or call.
APPLICATION USAGE
After a stream is associated with a pipe by the stream is byte-oriented (see orientation(5)).
RETURN VALUE
Upon successful completion, returns a pointer to an open stream that can be used to read or write to the pipe. Otherwise, it returns a
NULL pointer if files or processes cannot be created and set errno to indicate the error. The success of the command execution can be
checked by examining the return value of
Upon successful return, returns the termination status of the command language interpreter. Otherwise, returns -1 if stream is not associ-
ated with a command and set errno to indicate the error.
ERRORS
The function fails if:
The maximum number of file descriptors allowed are currently open.
The function fails if:
The status of the child process is not available.
WARNINGS
If the original and processes concurrently read or write a common file, neither should use buffered I/O because the buffering will not work
properly. Problems with an output filter can be forestalled by careful buffer flushing, e.g., with see fclose(3S).
SEE ALSO pipe(2), wait(2), fclose(3S), fopen(3S), system(3S), orientation(5), thread_safety(5).
STANDARDS CONFORMANCE popen(3S)