Programming ::make AWK Do *something* Without Giving It Any Stdin Nor Inputfile?
Oct 10, 2010
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I've given the output from `df` on AWK's stdin. But what I wonder is if there's a way to get AWK to run `df` itself, produce the same output, and exit? Doesn't seem to be that simple. Here's some examples: Works for some reason, and I think only in Bash (nothing is required in the $()
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does AWK absolutely need *something* on stdin, before it begins to process the data? Can it be made to open a file or stream internally, act upon that as though it were the stdin, and exit?
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Jun 22, 2010
Often in bash we read lines from stdin in a loop and implicitly discard the remaining stdin by terminating the loop. Is it possible to discard it without terminating the loop? It could lead to smaller code.
Here's an example which uses two loops and below is the same algorithm assuming unwanted stdin can be discarded
Code:
found=
while read destination gateway _
do
[[ $destination = default ]] && found=yes && break
done <<< "$( route )"
[Code].....
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Mar 14, 2010
I have a small program that reads stdin from a pipe using fgets. Now fgets blocks for the first line but after that it will not block.
The code, my_echo.c -
int main(int argc, char **argv) { char buf [2000] ;
char* pc ; printf("hello ") ; while (1)
{ buf[0] = (char) 0 ;
pc = fgets(buf, sizeof(buf), stdin);
if (pc != NULL) printf("%s ",buf); } return 0; }
How its called
* In terminal window 1: ./my_echo < my_fifo
* In terminal window 2: echo "1234" > my_fifo
* In terminal window 1: prints hello then 1234.
* Checking with ksysguard or top shows that my_echo is consuming 40% of CPU time.
Adding a few printf's shows that the gets is not blocking and returns a null pointer.
* In terminal window 2: echo "qwerty" > my_fifo
* In terminal window 1 qwerty prints.
I want a read function that does in fact block so my program does not tie up CPU time, read does not block.
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Dec 15, 2008
I need to write a script which will get a number from STDIN and then with that number echo a set number of questions (its for a firewall config). Heres what I want the user to receive.
How many ports do you want open? 3
1. specify port: 80
2. specify port: 21
3. specify port: 23
In the background this will echo a command out to a text file which will read as follows:
open port 80
open port 21
open port 23
I've done this before but I've completely forgotten how
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Aug 18, 2010
I'm trying to write a shell script that do ftp and download file periodically, this script should be called by a daemon running in the background.
the shell script "script.sh" is as follows:
Code:
yafc ftp://test:test@192.168.1.225:21 < commands
and the "commands" files is
Code:
d Root/md5* /
quit
if I run script.sh it will work just fine. But when the daemon software calls the "script.sh", the script will send ftp login request to the ftp server, but will not even answer the username or anything.
I believe it is something about child process redirection, but I don't know how to deal with it.
This problem is not only with yafc, it is the same with any ftp client or any application like telnet and so.
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Apr 28, 2010
I am trying to read one line at a time in perl and not wait for stdin eof to start the action:
Code:
foreach(<STDIN>){
<do something>
}
if i pipe ls into it, it waits for ls to be done before doing the action.
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Oct 20, 2010
I want to put a keystroke into another virtual terminal's stdin.A simple 'echo p > /dev/tty7' causes a p to appear on the console of tty7 but not the app running in tty7 to respond as though a p key had been pressed. Per the instructions of a fellow in the software forum I tried using an ioctl, but that returned a permissions error, even when I made the target VT's permissions 777 (and it had the same owner).
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Nov 24, 2010
I'm trying to write a program that will fork a series of FTP sessions. For each session, there should be separate input and output files associated with stdin and stdout/stderr.
I keep reading how I should be able to do that with dup2() in the child process before the execl(), but it's not working for me. Could someone please explain what I've done wrong? The program also has a 30-second sniper alarm for testing and killing of FTPs that go dormant for too long.
The code: (ftpmon.c)
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
[code]....
The output:
$ ftpmon
Connected to gila-crstest.gilacorp.com (172.16.20.8).
220 (vsFTPd 2.0.1)
ftp> waitpid(): Interrupted system call
Why am I getting the ftp> prompt? If the dup2() works, shouldn't it be taking input from my script and not my terminal? In stead, it does nothing, and winds up getting killed after 30 seconds. The log file is created, but it's empty after the run.
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Aug 8, 2010
I'm working on an application used for backup/archiving. That can be archiving contents on block devices, tapes, as well as regular files. The application stores data in hard packed low redundancy heaps with multiple indexes pointing out uniquely stored, (shared), fractions in the heap.
And the application supports taking and reverting to snapshot of total storage on several computers running different OS, as well as simply taking on archiving of single files. It uses hamming code diversity to defeat the disk rot, instead of using raid arrays which has proven to become pretty much useless when the arrays climb over some terabytes in size. It is intended to be a distributed CMS (content management system) for a diversity of platforms, with focus on secure storage/archiving. i have a unix shell tool that acts like gzip, cat, dd etc in being able to pipe data between applications.
Example:
dd if=/dev/sda bs=1b | gzip -cq > my.sda.raw.gz
the tool can handle different files in a struct array, like:
Code:
enum FilesOpenStatusValue {
FileIsClosed = 0,
FileIsOpen,
[code]....
Is there a better way of getting the file name of the redirected file, (respecting the fact that there may not always exist such a thing as a file name for a redirection pipe).
Should i work with inodes instead, and then take a completely different approach when porting to non-unix platforms? Why isn't there a system call like get_filename(stdin); ?
If you have any input on this, or some questions, then please don't hesitate to post in this thread. To add some offtopic to the thread - Here is a performance tip: When doing data shuffling on streams one should avoid just using some arbitrary record length, (like 512 bytes). Use stat() to get the recommended block size in stat.st_blksize and use copy buffers of that size to get optimal throughput in your programs.
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Sep 7, 2010
I'm writing a script to execute bash commands in the PHP CLI. I would like to suppress errors from bash and write my own error message if an error occurs. So far I have this (assuming log.txt doesn't exist!):
Code:
tac log.txt 2>/dev/null
Which works as expected, tac kicks up an error but the error is suppressed, but when I use this:
Code:
tac < log.txt 2>/dev/null
I get:
Code:
bash: log.txt: No such file or directory
The tac error is suppressed but bash still gives me a dirty error.
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Aug 4, 2011
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why is this? make menuconfig giving error
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Jan 8, 2010
Code:
#!/usr/bin/perl
use 5.10.0;
use strict;
use warnings;
use Net::Ping;
[code]....
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Jun 20, 2010
i m using atoi() to convert char value to int. and then passing that int as a swtich variable.switch goes in a case and exectuing that particualr function but returning 0 value....for example: i am finding no of process() and system up time().when switch program goes in system up time it gives right values means correct no of days, hrs , min and sec but when it goes in no of process() it gives 0 answer.
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Mar 29, 2010
ok not done this b4, so i google away, and get this! [URL]... from here [URL]... all it seems to do is give me a black screen. i would like some simple code for now, just to play the video. I can make a still for the link. I do't care if it's js, html, anything that works.
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Sep 7, 2010
While making a shell ,there is the following problem Im facing:
I am expecting the user to enter commands in the following format :
I am to separate these and the output of ls -l should be given as input to grep and the output of both to more.
But I am allowed (by our instructor) to use dup/dup2 or any other command(but not pipe or tees).
How to connect the file descriptors after successful execution of each command?
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Dec 25, 2010
My program is to find the values of variables using matrices and in matrices using GAUSS ELIMINATION method. It gives segmentation fault then I input the values of coefficients of the variables.
#include<stdio.h>
void main()
{
int n;
int i,j,l;
float m;
[Code]...
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Sep 23, 2010
I wrote a program to create a link list
Code:
#include <stdio.h>
#include <stdlib.h>
struct node {
[Code].....
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Mar 18, 2011
I am making online Myproject using java in which you can make your porject online or with your team, my problem is that when i drag one component from one page it disappear from another frame & i am unable to solve the problem that if the user don't have install java than myproject in not useable i am giving a span sort of code of my project:
[code]...
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Apr 12, 2010
I have a bash script giving me the following error:
[Code]...
When I run it I am getting: ./svnup: line 61: syntax error: unexpected end of file Can't for the life of me figure out what is wrong. It's a script to export the latest revision from SVN to the web root folder and archive the previous version, basically.
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Sep 15, 2010
I want to gave much details as possible. working directory (~/a1/shell) in the shell directory i have Makefile. also in the shell directory i have subdirectory's (obj, src, include)
My current Makefile
Quote:
#What needs to be built to make all files and dependencies
clean:
# End of Makefile
I wanted it so: all .o files are created in the obj subdirectory, and my application, sshell, is created in the shell directory.
I am getting this error when i run the make run: No rule to make target 'shell.h', needed by 'shutil.o'. stop
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Jan 15, 2011
I am intended to simply make printf give "001 002 003 004 006.... 150" but with the single command line of SH (dash) ... not easy ...
Code:
tucholsky:~$ seq 1 1 150 | sed 's/([0-9]+).*/1/g' | tr '
' ' '
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
[code]...
For the geeks, which distro/version is it, based on the code above
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Apr 8, 2010
While trying to compile one of the software application I am giving "cmake ." command but getting the below error :
I have downloaded "libpqxx-3.0.2" and have installed it.
libpqxx.a and libpqxx.la have got installed under /usr/local/lib.
Why am I still getting this error?
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Nov 26, 2008
I tried googling but didn't get any answer for this.I have a process called "abc" and it is running with PID "123".I have a putty session opened with PID "999".I am giving kill -TERM 123 from putty session.My process "abc" before dying it should catch the PID of the terminal which provided TERM signal to it.Is there any way to find this out
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Sep 26, 2010
I execute an application from a script file and redirect stdin to it from here-doc like this:
my_cli << HERE_DOC
enable
configure
10
exit
exit
HERE_DOC
This works as expected, but I don't see neither the input nor the app output. The application is an interactive prompt written in C. When I interact manually with it, I see the prompt itself and responses to my input, but when I execute the aforementioned script I see nothing. I would like it to print the input and the output as if a real user was typing. Do you know how to achieve that?
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Apr 28, 2011
I have the following bash script:
#do some time consuming task here read -p "Give me some input: " input
Now as you might've guessed, if users press some random keys during the "time consuming task," they're read into input as well. how do I clear stdin (or at least ignore it) before I issue the read command?
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Mar 7, 2011
i've tryed to get rid of the ugly plymouth splash screen and this outpout at boot now:
stdin: error 0
and so on... It also appears in my /var/log/boot.log and /var/log/casper.log. But the OS works, just like before. I would like to know how can i get rid of this error. Or how can i hide it? Can i redirect the output to dev null at boot time?
Here is boot.log
Code:
stdin: error 0
Generating locales...
sl_SI.UTF-8... up-to-date
Generation complete.
[Code]....
Because it is really annoying to see an "error" when your computer boots, even if it is not really an error
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Jul 28, 2010
I am trying to write input to a shell and get the shell to parse the input that I am writing to it as if a user was typing in commands.
Thus far I have tried echoing some text into the shell's FD for STDIN in /proc/<pid>/fd Whilst this displays the text that I echo, the shell that I am writing to never tries to execute the command that I pass to STDIN. What is the difference between a shell taking STDIN from the user and data written to STDIN by another process e.g. echo ? It appears I am missing something fundamental.
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Jun 28, 2010
Is it possible to redirect stdout and stderr from one terminal say /dev/pts/2 to another /dev/pts/3?
I tried the following:
Code:
/dev/pts/2 2>&1 /dev/pts/3&
Then when I run a command the process stops.
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Oct 19, 2010
causes a 'p' to appear in tty7 but not the program running in 7 to react as though a 'p' had been pressed.
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Jun 18, 2011
I have two Debian machines running Squeeze x86 and x86_64.
I am having difficulties to untar a file in x86_64, although it is working in x86.
I made sure file is the same and the md5 match in both machines.
It seems like something special in x86_64 is causing it to fail.
See below:
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