This is the result, (including the missing 'if'):
I am getting good at _fudging_ with single and double quotes.
But unless I use my Linux box I only have bash version 3.2.x, but almost everyone has POSIX compliance. <wink>
-------------------------
OT, in fact I used a method of exiting AudioScope.sh that was perfect until bash 4.4.x when someone must have noticed it was a serious bug and I thought it was a feature, post #7: AudioScope Project.
EDIT:
My modified version also works in 'dash'.
Last edited by wisecracker; 10-23-2019 at 06:01 AM..
Reason: See EDIT:
hi all, i have the following problem using awk in a script
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Hai,
Can you please guide me, to compare the floating point numbers.
Eg.
If
then
echo "value1 is grater "
fi
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Hi All,
I'm trying to extract some floating point numbers from within some HTML code like this:
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Hi guys
I have problem with my simple calculator, author of my book wrote
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Hi Everyone ,
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Heyas
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Discussion started by: sea
9 Replies
LEARN ABOUT CENTOS
system
SYSTEM(3) Linux Programmer's Manual SYSTEM(3)NAME
system - execute a shell command
SYNOPSIS
#include <stdlib.h>
int system(const char *command);
DESCRIPTION
system() executes a command specified in command by calling /bin/sh -c command, 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(2) 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 command 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
C89, C99, POSIX.1-2001.
NOTES
If the _XOPEN_SOURCE feature test macro is defined (before including any header files), then the macros described in wait(2) (WEXITSTA-
TUS(), etc.) are made available when including <stdlib.h>.
As mentioned, system() ignores SIGINT and SIGQUIT. This may make programs that call it from a loop uninterruptible, 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 set-user-ID or set-group-ID 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 set-user-ID or set-group-ID 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.)
In versions of glibc before 2.1.3, the check for the availability of /bin/sh was not actually performed if command was NULL; instead it was
always assumed to be available, and system() always returned 1 in this case. Since glibc 2.1.3, this check is performed because, even
though POSIX.1-2001 requires a conforming implementation to provide a shell, that shell may not be available or executable if the calling
program has previously called chroot(2) (which is not specified by POSIX.1-2001).
It is possible for the shell command to return 127, so that code is not a sure indication that the execve(2) call failed.
SEE ALSO sh(1), signal(2), wait(2), exec(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/.
2010-09-10 SYSTEM(3)