i've checked the link, and it makes it better. but it doesn't include all the information. i'll continue searching the internet. However i have seen an example of creating a fd:
as in the page, this was intended to redirect the stdout to the fd 5 and create it, and close it. i have the following questions:
- what is exactly the meaning of second command? is it to redirect the command stdout "test" to the fd 5? and how i can see the contents of the fd 5?
- in the first command, why the < is used instead if > and what is the difference between the below two commands as in the info bash *Redirection section
The redirection operator
[N]<&WORD
is used to duplicate input file descriptors. If WORD expands to one
or more digits, the file descriptor denoted by N is made to be a copy
of that file descriptor. If the digits in WORD do not specify a file
descriptor open for input, a redirection error occurs. If WORD
evaluates to `-', file descriptor N is closed. If N is not specified,
the standard input (file descriptor 0) is used.
The operator
[N]>&WORD
is used similarly to duplicate output file descriptors. If N is not
specified, the standard output (file descriptor 1) is used. If the
digits in WORD do not specify a file descriptor open for output, a
redirection error occurs. As a special case, if N is omitted, and WORD
does not expand to one or more digits, the standard output and standard
error are redirected as described previously.
I am trying to find a way to check the current status of a file. Such as some cron job processes are dependent on the completion of others. if a file is currently being accessed / modified or simply open state I will wait until it is done being processed before attempting the next process on that... (3 Replies)
Hello All,
Im opening a file desciptor in perl and sending data using print CMD "$xyz".
is there a limit to the length of the string that I can give to this CMD at a time. (3 Replies)
I have a file, let's say 1.jpg, and I have a text file that contains a list of filenames I would like to duplicate 1.jpg as (i.e., 2.jpg, 3.jpg, 4.jpg, etc.). The filenames that I want to create are all on separate lines, one per line.
I'm sure there's a simple solution, but I'm not claiming to... (7 Replies)
I am trying to use one global declaration --> "exec 2>$ERR" to capture all stderr outputs that may occur anywhere in my script.
Then close it at the end of the script using --> "exec 2<&-"
I am using KSH on Solaris 8.
KSH Version M-11/16/88i
If I comment two "exec .." statements in the... (11 Replies)
Hi,
I am trying to read a file line-by-line in a while loop, and perform some tasks which involves non-interactive SSH to a remote server. The code looks something like this --
#!/usr/bin/ksh
export myFile=/path/to/my/file.load
while read line
do
do something
## Adding the SSH... (2 Replies)
Greetings.
I am happily using constructs like the following; I have set -x to show fine distinctions.
$ exec 4> afile
+ exec
+ 4> afile
$ print -u4 This is the first line in afileAs you can see from the -x expansion, the shell performed the exec command and redirected file descriptor to... (4 Replies)
I have a shell script with 2 run time arguments. During the execution if i got any error, then it needs to redirected to a error file and in console. Also both error and output to be redirected to a log file.
Error output is getting copied to err file and getting displayed in console too. But... (2 Replies)
Discussion started by: sarathy_a35
2 Replies
LEARN ABOUT ULTRIX
exec
exec(1) User Commands exec(1)NAME
exec, eval, source - shell built-in functions to execute other commands
SYNOPSIS
sh
exec [argument...]
eval [argument...]
csh
exec command
eval argument...
source [-h] name
ksh
*exec [arg...]
*eval [arg...]
DESCRIPTION
sh
The exec command specified by the arguments is executed in place of this shell without creating a new process. Input/output arguments may
appear and, if no other arguments are given, cause the shell input/output to be modified.
The arguments to the eval built-in are read as input to the shell and the resulting command(s) executed.
csh
exec executes command in place of the current shell, which terminates.
eval reads its arguments as input to the shell and executes the resulting command(s). This is usually used to execute commands generated as
the result of command or variable substitution.
source reads commands from name. source commands may be nested, but if they are nested too deeply the shell may run out of file descrip-
tors. An error in a sourced file at any level terminates all nested source commands.
-h Place commands from the file name on the history list without executing them.
ksh
With the exec built-in, if arg is given, the command specified by the arguments is executed in place of this shell without creating a new
process. Input/output arguments may appear and affect the current process. If no arguments are given the effect of this command is to mod-
ify file descriptors as prescribed by the input/output redirection list. In this case, any file descriptor numbers greater than 2 that are
opened with this mechanism are closed when invoking another program.
The arguments to eval are read as input to the shell and the resulting command(s) executed.
On this man page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways:
1. Variable assignment lists preceding the command remain in effect when the command completes.
2. I/O redirections are processed after variable assignments.
3. Errors cause a script that contains them to abort.
4. Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a vari-
able assignment. This means that tilde substitution is performed after the = sign and word splitting and file name generation are not
performed.
EXIT STATUS
For ksh:
If command is not found, the exit status is 127. If command is found, but is not an executable utility, the exit status is 126. If a redi-
rection error occurs, the shell exits with a value in the range 1-125. Otherwise, exec returns a zero exit status.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWcsu |
+-----------------------------+-----------------------------+
SEE ALSO csh(1), ksh(1), sh(1), attributes(5)SunOS 5.10 17 Jul 2002 exec(1)