I had different problem scenarios with IF statement. Can any expert please enlighten me on the difference with these scenarios. Thank you.
1st Scenario:
testdate=`date +%Y%m`
test=`cat /var/log/database0.$testdate*.log | grep "Errors found during processing" | tail -10`
if
then
... (4 Replies)
I am kind of new in Unix and i have to make a menu. I want to put an if statement in the menu. you should enter the filename and it goes to that file. How do i do this? (1 Reply)
Good morning all!
I want to know if Im interpreting this if statement below right.
if(((1) || (0)) && (1)){
do stuff;
}
This is saying: if true piped into false, then true, then do stuff. Right?
What does the && stand for?
thanks in advance!
ben (3 Replies)
Hi
I am very new to Unix programming and shell scripting. I am trying t figure out how to write a little script that will output the number of directories. I can find the number of directories using ls -l | grep "^d" | wc -l I can not figure out how to do it so when I type the name... (8 Replies)
1. The problem statement, all variables and given/known data:
Two problems I need solving please. I created a script where the user types in 7 numbers as standard input and each one is then stored in an array. Now I need to perform the following calculations on those numbers:
1) Use a while... (11 Replies)
I came across a bash script that outputs the forecast for the day and the max temperature but at the end of the day the max temperature disappears ($6) and I am left with "°C" after the forecast.
Here is the script:
#! /bin/bash
curl -s --connect-timeout 30... (7 Replies)
Hello all!
This is my first post and I'm very new to programming. I would like help creating a simple perl or bash script that I will be using in my work as a junior bioinformatician.
Essentially, I would like to take a tab-delimted or .csv text with 3 columns and write them to a "3D" matrix:
... (16 Replies)
Cheers!
In /etc/syslog.conf, if an error type is not specified, is it logged anywhere (most preferable is it logged to /var/log/messages) or not?
To be more precise I am interested in error and critical level messages. At default these errors are not specified in syslog.conf, and I need to... (6 Replies)
Discussion started by: dr1zzt3r
6 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)