08-21-2018
I have been struggling with bash for less than a month now.
The idea was to use existing bash script and ADD some functionality to it.
When I do coding I like to keep my attempts in code so I do not repeat it.
So I am spoiled by C ability to comment out block of code and found that using "cut" can be used in bash. Unfortunately I have learn the "#" used at the bash scrip in this fashion #!... is really not "commented out line " - so this "problem using "cut" may be same issue.
BTW I did build a simple test function and using two "cut' in succession works just fine - that is not the issue.
I have been writing "code" for few years and firmly believe the "computer" will skip commented out code as instructed and it really does not bother me I my code contains code which is NOT executed one way or another.
Right now my code just "exit"s before getting to offending code.
I will try to analyze / delete the offending code to get rid of this error.
4 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
Hello,
Could you put some light on this:
> echo "ref_categorie=test" | cut -c1-15-
test
> echo "ref_categorie=test" | cut -c1-14-
=test
echo "ref_categorie=test" | cut -c15-
test
echo "ref_categorie=test" | cut -c15
t
>
It's executed on AIX if that matters. The man page is not very... (2 Replies)
Discussion started by: tsurko
2 Replies
2. Shell Programming and Scripting
Hi all,
I'm trying to extract string from variable in BASH. That's probably trivial for grep but I couldn't figure it out.
I want to get name, there's sometimes digit after it, but it should be left out.
STRING=http://name5.domain.com:8000/file.dat
Could someone help me with that?
Any... (10 Replies)
Discussion started by: cootue
10 Replies
3. Shell Programming and Scripting
Hi
Can anyone what I am doing wrong while using cut command.
for f in *.log
do
logfilename=$f
Log "Log file Name: $logfilename"
logfile1=`basename $logfilename .log`
flength=${#logfile1}
Log "file length $flength"
from_length=$(($flength - 15))
Log "from... (2 Replies)
Discussion started by: dgmm
2 Replies
4. UNIX for Beginners Questions & Answers
I'm a complete beginner in UNIX (and not a computer science student either), just undergoing a tutoring course. Trying to replicate the instructions on my own I directed output of the ls listing command (lists all files of my home directory ) to My_dir.tsv file (see the screenshot) to make use of... (9 Replies)
Discussion started by: scrutinizerix
9 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)