This is a common problem. When you run the command, the output file is opened (and overwritten) before you start to read the input, which by now is null. You command then exists as it finishes reading no input.
You will need to read the input and write to a separate output file. If need be, then rename (and overwrite) the input file thus:-
Code:
sort -o output input
mv output input
It does mean that you have to consider space for having the two files at the same time, even if just for a moment.
Hi,
What are the contents of /var/sadm/pkg/<pkg>/save directory.
- It contains various patches with their id's.
What does the "pspool" directory inside it contain? (6 Replies)
Hi,
How to add string inside the file. In this case adding 63 in the beginning of each line. Thnks.
e.g. what is inside the file
Mobile Number Portability
9051151234
9051261345
9051393245
9051412345
9051507654
should like this as output:
Mobile Number Portability (7 Replies)
I'm using the following script to check cisco router health and I'd like to save output to a file,
vty_runcmd.sh > /check/check-cisco-health
script works and output is saved to a file. However using it in crontab file is created but output is not printed inside it. In crontab,
*/5 * * * *... (4 Replies)
I have the file sed1.txt and I need to strip the brackets (]) and content inside them only when
I have two or three letters followed by a colon.
for example,it may be any letter, not just abc
]
]
#-- cat sed1.txt
1 ] FISICA
2 ]PORTUGUES
3 ] ]MATEMATICA
4 ]]INGLES ]
5 ]QUIMICA
6... (2 Replies)
I need that a certain part of the content below excluded
==Image Gallery== followed by <gallery> and the content until </gallery>
test SED1
==Image Gallery==
<gallery>
Image:car1.jpg| Car 1<sup>1</sup>
Imagem: car2.jpg| Car2<sup>2</sup>
</gallery> test SED2
==Image... (5 Replies)
Hello,
I'm using Windows 7 ; sed, awk and gnuwin32 are installed.
I have a big text file I need to manipulate.
In short, I will have to split it in thousands of short files, then rename and save in a folder which name is based upon filename.
Here is a snippet of my big input.txt file (this... (4 Replies)
Hi Team,
Not getting the file output inside my email which i am sending from unix box. . Please refer the below code :
#!/bin/sh
{
sleep 5
echo ehlo 10.56.185.13
sleep 3
echo mail from: oraairtel@CNDBMUREAPZP02.localdomain
sleep 3
echo rcpt to: saurabhtripathi@anniksystems.com... (1 Reply)
Hi,
Right now there is a file called 'qm.ini' which is owned by mqm:mqm and I am trying to replace a line from this file with something else and save.
I am using the below perl command to replace and save within a shell script with a different user called 'mqadm' which is also part of mqm... (1 Reply)
I have a script that sorts and processes unsorted files to newly created directories.
Its working great, but I am trying to understand the leanest method to get the script to create an additional file within each newly created directory that:
Contains a list of all files in the directory... (4 Replies)
Discussion started by: Braveheart
4 Replies
LEARN ABOUT BSD
popen
POPEN(3) Library Functions Manual POPEN(3)NAME
popen, pclose - initiate I/O to/from a process
SYNOPSIS
#include <stdio.h>
FILE *popen(command, type)
char *command, *type;
pclose(stream)
FILE *stream;
DESCRIPTION
The arguments to popen are pointers to null-terminated strings containing respectively a shell command line and an I/O mode, either "r" for
reading or "w" for writing. It creates a pipe between the calling process and the command to be executed. The value returned is a stream
pointer that can be used (as appropriate) to write to the standard input of the command or read from its standard output.
A stream opened by popen should be closed by pclose, which waits for the associated process to terminate and returns the exit status of the
command.
Because open files are shared, a type "r" command may be used as an input filter, and a type "w" as an output filter.
SEE ALSO pipe(2), fopen(3S), fclose(3S), system(3), wait(2), sh(1)DIAGNOSTICS
Popen returns a null pointer if files or processes cannot be created, or the shell cannot be accessed.
Pclose returns -1 if stream is not associated with a `popened' command.
BUGS
Buffered reading before opening an input filter may leave the standard input of that filter mispositioned. Similar problems with an output
filter may be forestalled by careful buffer flushing, for instance, with fflush, see fclose(3S).
Popen always calls sh, never calls csh.
7th Edition May 15, 1985 POPEN(3)