Bash IFS Post: 302697325

Sponsored Content

Top Forums Shell Programming and Scripting Bash IFS Post 302697325 by Corona688 on Thursday 6th of September 2012 02:16:53 PM

09-06-2012

Registered User

IFS works both ways. The shell splits strings apart on IFS, and when you put together a string with $*, it also puts them back together with IFS.

So, when you do ./myscript --xsrc 1234, $* actually turns it into --xsrc|1234. You just don't see it because you're letting the shell split it right back apart afterwards.

To prevent the shell from splitting something, you put it in quotes, so try this:

Code:

OLDIFS="$IFS"
IFS="|="                # IFS controls splitting. Split on "|" and "="
echo "$*"
set -- $*               # Set the positional parameters to the command line arg$
IFS="$OLDIFS"

Code:

$ ./script --arg=1234 # One argument

--arg=1234

$ ./script --arg 1234 # Two arguments

--arg|1234

$

So you see, the first time it comes in as 1 argument and nothing gets inserted by $*.

The second time it comes as two arguments, and gets stuck together into one string with | between.

IFS splits on both | and =, so set -- $* splits it apart where appropriate either way.

Last edited by Corona688; 09-06-2012 at 03:37 PM..

Corona688

View Public Profile for Corona688

Visit Corona688's homepage!

Find all posts by Corona688

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

IFS variable

How can I set the value for IFS variable

2. Shell Programming and Scripting

problem with IFS

hi, :) I set IFS=":" But when i try to echo $IFS,i am not getting any thing on the screen escept a blank line. any help pls. cheers RRK

3. Shell Programming and Scripting

regarding IFS=

hi i am a learner can some explain "export IFS=$(echo "\n\t\a")" i am not able to understand the functionality please help thanks Satya

4. Shell Programming and Scripting

while loop with 3 ifs

im messing up somehwere...and can't seem to clean up the script...for it to work objectives: 1. check for today's file, and sleep 30 secs between retries 2. only allow 5 tries before script should fail. 3. if today's file found, wait 30 seconds for it to process.. code: count=0...

5. Shell Programming and Scripting

read and IFS

Hi, This is out of curiosity: I wanted to extract year, month and date from a variable, and thought that combining read and IFS would help, but this doesn't work: echo "2010 10 12" | read y m d I could extract the parts of the date when separated by a -, and setting IFS in a subshell: ...

6. Shell Programming and Scripting

How to use IFS in this scenario?

Given the scenario like this, if at all if have to use IFS on the below given example, how it should be used. IFS=/ eg: /xyz/123/348/file1 I want to use the last slash /file1 . So can anyone, suggest me how to pick the last "/" as a IFS.

7. Shell Programming and Scripting

Not able to understand IFS

Hi , i am in my initial learning phase of unix. i was going thru the function part. below is the example which was there but i am not able to understand logic and the use of IFS(internal field separator) lspath() { OLDIFS="$IFS" IFS=: for DIR in $PATH ; do echo $DIR ; done IFS="$OLDIFS"...

8. Shell Programming and Scripting

Changing IFS in bash function

I have a function in bash that takes arguments. does IFS work in a function or does it apply only to the main script?

9. Shell Programming and Scripting

Remote while IFS

Hello masters of scripting, I've been working to develop some basic monitoring scripts. I have solved one problem, but want to know how to solve the other. I have a script that runs locally to create an output file with the Linux system kernel paramters, preceeded by the system name: ...

10. Shell Programming and Scripting

Bash : More parameter expansion and IFS

I am trying to become more fluent with the interworking of bash and minimize the number of external calls. Sample Data. This will be the response of the snmp query. SNMPv2-MIB::sysName.0 = STRING: SomeHostName SNMPv2-MIB::sysObjectID.0 = OID: SNMPv2-SMI::enterprises.9.1.1745...

LEARN ABOUT DEBIAN

ns_getsockaddr

Ns_Sock(3aolserver)					   AOLserver Library Procedures 				       Ns_Sock(3aolserver)

__________________________________________________________________________________________________________________________________________________

NAME

       Ns_BindSock,  Ns_GetSockAddr,  Ns_SockAccept,  Ns_SockAsyncConnect,  Ns_SockAsyncConnect2,  Ns_SockBind, Ns_SockCloseLater, Ns_SockConnect,
       Ns_SockConnect2, Ns_SockListen, Ns_SockListenEx, Ns_SockPipe, Ns_SockSetBlocking, Ns_SockSetNonBlocking, Ns_SockStrError,  Ns_SockTimedCon-
       nect, Ns_SockTimedConnect2, ns_pipe, ns_sockpair - library procedures

SYNOPSIS

       #include "ns.h"

       Ns_BindSock(arg, arg)

       Ns_GetSockAddr(arg, arg)

       Ns_SockAccept(arg, arg)

       Ns_SockAsyncConnect(arg, arg)

       Ns_SockAsyncConnect2(arg, arg)

       Ns_SockBind(arg, arg)

       Ns_SockCloseLater(arg, arg)

       Ns_SockConnect(arg, arg)

       Ns_SockConnect2(arg, arg)

       Ns_SockListen(arg, arg)

       Ns_SockListenEx(arg, arg)

       Ns_SockPipe(arg, arg)

       Ns_SockSetBlocking(arg, arg)

       Ns_SockSetNonBlocking(arg, arg)

       Ns_SockStrError(arg, arg)

       Ns_SockTimedConnect(arg, arg)

       Ns_SockTimedConnect2(arg, arg)

       ns_pipe(arg, arg)

       ns_sockpair(arg, arg)
_________________________________________________________________

DESCRIPTION

       These functions ...

SEE ALSO

       nsd(1), info(n)

KEYWORDS

AOLserver								4.0						       Ns_Sock(3aolserver)

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

IFS variable

Discussion started by: mahabunta

2. Shell Programming and Scripting

problem with IFS

Discussion started by: ravi raj kumar

3. Shell Programming and Scripting

regarding IFS=

Discussion started by: Satyak

4. Shell Programming and Scripting

while loop with 3 ifs

Discussion started by: sigh2010