In fact there is and i am glad to be able to explain - once in a lifetime - "super advanced system admin expert methods" to the audience: You can redirect output streams with the "exec" command:
exec 2>output.stderr
Will redirect every output of every subsequent command to output.stderr.
This way you do not have to worry about truncating the file at all:
Code:
exec 2>output.stderr # truncates the file and redirects stderr to it
job1
job2
job3
exec 2>&- # closes stderr and removes the redirection
I am using the time command in a script however the output of the time command will display on my screen but not my output file. Any Ideas on how to fix this?
> cat test.sh
#############################
#!/usr/bin/sh
for COMMAND in pwd
do
time ${COMMAND}
done | sed "s/^/ ... (4 Replies)
I am using ksh on an AIX box.
I would like to redirect the stdout and stderr to a file but also show them on the terminal. Is this possible? I have tried tee within my file without success.
This is the code I have so far
exec > imp.log 2>&1 | tee exec 1>&1
I am new to shell scripting, so... (3 Replies)
exam is a ksh script. In command line I enter: exam 3 param_2 param_3 param_4.
In exam how can I get the value of the parameter which position is specified by the first argument.
Simply doing this DOES NOT work:
offset=$1
value=$$offset
can you figure out any possible way to interpret a... (5 Replies)
Hello all,
I have a script that I am trying to execute and redirect the output to a file, but I have trouble in redirection. The cron job is running properly as I see it in the mail.
This is what I am doing
In crontab file,
0 4 * * * somescript.sh > /some_location/`date '+%m%d%y_%H%M'`.log... (9 Replies)
Hi,
I need to create one KSH which will send mail to set of recipients using "mailx" command like below.
mailx -s "Test mail" "test@yahoo.com, test@gmail.com" <$output.txt
The recipients are in different domains (like yahoo, gmail, etc.).
My requirement is, if any mail is undelivered,... (1 Reply)
Hi,
I have perl script which is calling an external command using "system()" with argument.
But i am not able to capture the output.Even tried with backtick also with no luck.
.
.
$number=<>;
system ("cmd $number >output.txt"); (2 Replies)
Hello,
i'm trying to implement the times() function and i'm programming in C.
I'm using the "struct tms" structure which consists of the fields:
The tms_utime structure member is the CPU time charged for the execution of user instructions of the calling process.
The tms_stime structure... (1 Reply)
I have a script to send an email like below. Problem is, the if ..fi block is not getting executed, and is coming as a part of the email body. Can anyone take a look at this? :confused:
Log file shows this:
SEND_MAIL.prog: line 64:
: command not found
echo "Input Parameters"
echo... (11 Replies)
Hello all,
I would like to create a for loop or whatever is quick that will print the one’s place of a number for 1-N times
say for example a printed page formatting is 132 characters wide,
I would like a single line
123456789012345678901234567890... ...012
That is 132 characters long. I... (11 Replies)
Hi
Please can you help how do I count the number of specific characters or words that appear in a file? (8 Replies)
Discussion started by: fretagi
8 Replies
LEARN ABOUT CENTOS
stdin
STDIN(3) Linux Programmer's Manual STDIN(3)NAME
stdin, stdout, stderr - standard I/O streams
SYNOPSIS
#include <stdio.h>
extern FILE *stdin;
extern FILE *stdout;
extern FILE *stderr;
DESCRIPTION
Under normal circumstances every UNIX program has three streams opened for it when it starts up, one for input, one for output, and one for
printing diagnostic or error messages. These are typically attached to the user's terminal (see tty(4) but might instead refer to files or
other devices, depending on what the parent process chose to set up. (See also the "Redirection" section of sh(1).)
The input stream is referred to as "standard input"; the output stream is referred to as "standard output"; and the error stream is
referred to as "standard error". These terms are abbreviated to form the symbols used to refer to these files, namely stdin, stdout, and
stderr.
Each of these symbols is a stdio(3) macro of type pointer to FILE, and can be used with functions like fprintf(3) or fread(3).
Since FILEs are a buffering wrapper around UNIX file descriptors, the same underlying files may also be accessed using the raw UNIX file
interface, that is, the functions like read(2) and lseek(2).
On program startup, the integer file descriptors associated with the streams stdin, stdout, and stderr are 0, 1, and 2, respectively. The
preprocessor symbols STDIN_FILENO, STDOUT_FILENO, and STDERR_FILENO are defined with these values in <unistd.h>. (Applying freopen(3) to
one of these streams can change the file descriptor number associated with the stream.)
Note that mixing use of FILEs and raw file descriptors can produce unexpected results and should generally be avoided. (For the masochis-
tic among you: POSIX.1, section 8.2.3, describes in detail how this interaction is supposed to work.) A general rule is that file descrip-
tors are handled in the kernel, while stdio is just a library. This means for example, that after an exec(3), the child inherits all open
file descriptors, but all old streams have become inaccessible.
Since the symbols stdin, stdout, and stderr are specified to be macros, assigning to them is nonportable. The standard streams can be made
to refer to different files with help of the library function freopen(3), specially introduced to make it possible to reassign stdin, std-
out, and stderr. The standard streams are closed by a call to exit(3) and by normal program termination.
CONFORMING TO
The stdin, stdout, and stderr macros conform to C89 and this standard also stipulates that these three streams shall be open at program
startup.
NOTES
The stream stderr is unbuffered. The stream stdout is line-buffered when it points to a terminal. Partial lines will not appear until
fflush(3) or exit(3) is called, or a newline is printed. This can produce unexpected results, especially with debugging output. The
buffering mode of the standard streams (or any other stream) can be changed using the setbuf(3) or setvbuf(3) call. Note that in case
stdin is associated with a terminal, there may also be input buffering in the terminal driver, entirely unrelated to stdio buffering.
(Indeed, normally terminal input is line buffered in the kernel.) This kernel input handling can be modified using calls like tcse-
tattr(3); see also stty(1), and termios(3).
SEE ALSO csh(1), sh(1), open(2), fopen(3), stdio(3)COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2008-07-14 STDIN(3)