This is the problematic line. After this variable expansion, parameter is set to the value "word" and then the shell will try to execute that command, which it can't find. I can't fathom why you need to use this. The following line will work:
** ${parameter:=word}
### when you first execute that and if parameter is null or not set then ksh genaretes an error but assigns to "word" to parameter value..
Code:
# ${parameter:=word}
ksh: word: not found.
# echo $parameter
word
### after that the first execute that command , then other executes ksh also genarete errors because of ksh executes for first argument ( ${parameter,,,,} ) so now parameter value's is "word",and returns the "word not found" error and then quit the executing process(shell internals)..
this same to that ( try this )
Code:
# word
ksh: word: not found.
** ${parameter:=$word}
### when you execute this , ksh runs successfully and because of parameter and word value is null already.. (so any change and no error )
Code:
# ${parameter:=$word}
#
### first try below command , ksh returns same results because of ksh wants to execute word value and then returns the error normally but
parameter value assings to "10", because paramater value is NULL for first try or when parameter is null
### other executes after than first , now parameter value was 10
and ksh tries to execute parameter value so "10" executed and then so ksh gives the error and quit from subsitution process in shell internal.
Code:
# ${parameter:=$word}
ksh: 10: not found.
** with echo
ksh and bash does not generate any errors and echoes the assigment results..
thx ygemic for detail info. this really help me a lot.
below is the script which i am using now. but after the highlighted part(in red color) script does not execute. however if i commented the highlighted part it will run the rest part of the script.
below is my script
Code:
> cat -n var_subs
1 #!/bin/ksh
2
3 ################################${parameter:-word} - If parameter is unset, substitute "word"
4
5
6 vk=
7 echo $vk
8 echo ${vk:-khare}$
9 echo $vk
10 ####################################################
11
12 ### ${parameter:?word} - Display "word" or error if parameter is unset
13 echo $vk
14 echo ${vk:?"NO"}
15 echo $vk
16
17
18
19 ##############################################################
20
21 ### ${parameter:=word} - If parameter is unset, set it to "word"
22 echo $vk
23 echo ${vk:=vai}$
24 echo $vk
25 ########################################################
26
27
28 ### ${parameter:+word} - "word" is substituted only if parameter is set
29
30 echo ${vk:+vaibhav}
31 echo $vk
the o/p of the above script is
Code:
> var_subs
khare$
var_subs[14]: vk: NO
the below is the o/p which i got after commenting the highlighted part.
Code:
> var_subs
khare$
vai$
vai
vaibhav
vai
no idea why this is happening.
Last edited by Scrutinizer; 07-12-2012 at 07:07 AM..
Reason: code tags
You need to read about variable expansion in korn before asking such questions.
Code:
${variable:-word}, ${variable-word}
This is expanded to the value of variable if it is set and not null, otherwise word is expanded.
This is used to provide a default value if a variable is not set.
The variable value remains unchanged.
-------
${variable:?word}, ${variable:?}, ${variable?word}, ${variable?}
This is expanded to the value of variable if it is set and not null, otherwise word is printed
and the Korn shell exits.
If word is omitted, 'parameter null or not set' is printed.
This feature is often used in Korn shell scripts to check if mandatory variables are set.
Hi ,
I was invoking a sh file using the nohup command. But while invoking, I received a below error.
Error occurred during initialization of VM
Unable to load native library: /u01/libjava.so: cannot open shared object file: No such file or directory
.
Could you please help out.
Regards,... (2 Replies)
Hallo Team,
I have a simple request and i would appreciate your help.
I would like to use two dates in my script lets:
A=$(date +"%d %B %Y")
echo $A
23 June 2014
That's awesome now we cooking. Now i want B to be on the previous month
eg: echo $B Should give me
23 May 2014
I would... (9 Replies)
Hi everybody,
my problem is the following:
I'm trying to run an openmpi program on a cluster (atlasz.elte.hu, it's in hungarian, but you can try google translate),
but I always got this error:
Fatal error in MPI_Init: Other MPI error, error stack:
MPIR_Init_thread(394)...........:... (0 Replies)
I get an error in my shell script that line 1: )unexpected.
Line 1 in my script (using sh by the way) is the variable I declared but did not initialize it.
result=
Is this wrong? How can I fix it? I am using the variable later in the program, so I figured I could just declare it first... (4 Replies)
Hello everyone,
I have a question, that are the following ways of pointer intialization same ?
ClassA *point;
point = 0;
point = new ClassA;
Thanks a load in advance!!
Regards, (10 Replies)
Hi All,
char a="\0";
a) a contains \0
a contains garbage value
b) a contains \
a contains 0
a contains garbage value
Pls, let me know correct result is a or b. I guess a.
Thanks,
Naga:cool: (2 Replies)
As you know, when a user logs in, the shell reads the initialization files in an order something like below...
###################
Bourne Shell
/etc/profile > $HOME/.profile
Bash Shell
/etc/profile > $HOME/.bash_profile > $HOME/.bash_login > $HOME/.profile > $HOME/.bashrc
C Shell... (3 Replies)
Hi all,
In my shell script, I am reading some files, processing them, and writing the out-put in the log files. The out put contains number of rows in the file etc.
I want to fetch the input files from a particular directory and I want to write the logs in a particular directory with a particular... (1 Reply)
Hi
We are using a code generator for initializing structures with the #define macro. Compiling it with the GCC 2.8.1 (with -ansi) it OK. But when we are using the SUN C 5.0 compiler it screams.
Following is a code sample:
#include <stdlib.h>
#include <stdio.h>
typedef struct TEST3 {... (4 Replies)
07-12-2012
