As Scrutinizer mentioned, with bash the commands after the pipe run in a subshell and variables in a subshell are not visible outside the block of code in the subshell and they are not accessible to the parent process.
You can avoid the use of a pipe (and useless use of cat) like:
my input file contains thousands of lines like below
234A dept of education
9788 dept of commerce
8677 dept of engineering
How do i add a delimeter ':' after FIRST 4 CHARACTERS in a line
234A:dept of education
9788:dept of commerce
8677:dept of engineering (7 Replies)
Hi All,
I am comparing two strings inside an if condition if the strings are same then it should go inside the loop else it should execute code given in else part.
But there is a but inside my script
Even if the if condition is true
it is not going inside the loop also it is executing... (4 Replies)
Hi All,
I need to concatenate the values in the array into a variable. Currently the code is :
for (( i=1 ; i <= $minCount ; i++ ))
do
var="${var}""${sample_file}"
done
The output is :
/tmp/1/tmp/2/tmp/3/tmp/4/tmp/5/tmp/6/tmp/7/tmp/8/tmp/9/tmp/10
I need a space between... (1 Reply)
Hi,
In the code included below, the string comparision is not working fine. Please help
while (( find_out >= i ))
do
file=`head -$i f.out|tail -1`
dir=`dirname $file`
cd $dir
Status=""
if ; then
Status=`cvs -Q status... (3 Replies)
The string comparison highlighted below is not working fine. Please help:
while read line
do
# Get File name by deleting everything that preceedes and follows Filename as printed in cvs status' output
f_name=`echo $line | sed -e 's/^File://' -e 's/ *Status:.*//' | awk '{print $NF}'`
... (4 Replies)
Hi there,
I'm writing a basic script where I want to make a string of 2 numeric fields from a file, which I have done, but the behavior is rather confusing.
I have a file of random values such as:
1 2
3 4
5 6
7 8
9 10
and my awk code is:
BEGIN { FS = " " }
{ str = str $1 $2 }
END {... (7 Replies)
Hello
I want to achieve the following.
However the concatenation is not working
mv `ls -ltr *myfile*.log|awk '{print $9}'` `ls -ltr *myfile*.log|awk '{print `date +'%d%m%y%k%M%S'` $9}'`
I tried
awk '{x=`date +'%d%m%y%k%M%S'` print $x "" $9}'
awk '{x=`date +'%d%m%y%k%M%S'`... (2 Replies)
Hi Team!!
Please can anyone tell me why the following line does not work properly?
str3+=$str2
it seems that str3 variable does not keep its value in order to be concatenated in the next iteration! Thus when i print the result of the line above it returns the str2 value
What i want to do is to... (8 Replies)
I have a script which is migrated from AIX to Linux & now while running it is no able to concatenate string values
The string concatenation step under while loop is not displaying desired result
Please find below the piece of code:
while read EXT_FILE ; do
EXT_FILE=$EXT_FILE.ext.sent
echo... (7 Replies)
Discussion started by: PreetArul
7 Replies
LEARN ABOUT REDHAT
system
SYSTEM(3) Linux Programmer's Manual SYSTEM(3)NAME
system - execute a shell command
SYNOPSIS
#include <stdlib.h>
int system(const char *string);
DESCRIPTION
system() executes a command specified in string by calling /bin/sh -c string, and returns after the command has been completed. During
execution of the command, SIGCHLD will be blocked, and SIGINT and SIGQUIT will be ignored.
RETURN VALUE
The value returned is -1 on error (e.g. fork failed), and the return status of the command otherwise. This latter return status is in the
format specified in wait(2). Thus, the exit code of the command will be WEXITSTATUS(status). In case /bin/sh could not be executed, the
exit status will be that of a command that does exit(127).
If the value of string is NULL, system() returns nonzero if the shell is available, and zero if not.
system() does not affect the wait status of any other children.
CONFORMING TO
ANSI C, POSIX.2, BSD 4.3
NOTES
As mentioned, system() ignores SIGINT and SIGQUIT. This may make programs that call it from a loop uninterruptable, unless they take care
themselves to check the exit status of the child. E.g.
while(something) {
int ret = system("foo");
if (WIFSIGNALED(ret) &&
(WTERMSIG(ret) == SIGINT || WTERMSIG(ret) == SIGQUIT))
break;
}
Do not use system() from a program with suid or sgid privileges, because strange values for some environment variables might be used to
subvert system integrity. Use the exec(3) family of functions instead, but not execlp(3) or execvp(3). system() will not, in fact, work
properly from programs with suid or sgid privileges on systems on which /bin/sh is bash version 2, since bash 2 drops privileges on
startup. (Debian uses a modified bash which does not do this when invoked as sh.)
The check for the availability of /bin/sh is not actually performed; it is always assumed to be available. ISO C specifies the check, but
POSIX.2 specifies that the return shall always be non-zero, since a system without the shell is not conforming, and it is this that is
implemented.
It is possible for the shell command to return 127, so that code is not a sure indication that the execve() call failed.
SEE ALSO sh(1), signal(2), wait(2), exec(3)
2001-09-23 SYSTEM(3)