IFS Internal Field Separator — GNU Bash.

$ 4.2.36 1 501---> echo $*

$ 4.2.36 2 502---> echo "$*"

$ 4.2.36 3 503---> echo $IFS

$ 4.2.36 4 504---> set $IFS=rightleftwrong
$ 4.2.36 5 505---> echo $*
=rightleftwrong
$ 4.2.36 6 506---> echo "$*"
=rightleftwrong
$ 4.2.36 7 507---> echo $IFS

$ 4.2.36 8 508---> echo $*
=rightleftwrong
$ 4.2.36 9 509---> read $*
jeff
bash: read: `=rightleftwrong': not a valid identifier
$ 4.2.36 10 510---> read $*
bash: read: `=rightleftwrong': not a valid identifier
$ 4.2.36 11 511---> read $*;
bash: read: `=rightleftwrong': not a valid identifier
$ 4.2.36 12 512--->  var1=1+2+3
$ 4.2.36 13 513---> echo $var1
1+2+3
$ 4.2.36 14 514---> IFS=+
$ 4.2.36 15 515---> echo $var1
1 2 3
$ 4.2.36 16 516---> IFS=-
$ 4.2.36 17 517---> echo $var1
1+2+3
$ 4.2.36 18 518---> IFS=" "
$ 4.2.36 19 519---> echo $var1
1+2+3
$ 4.2.36 20 520---> IFS=","
$ 4.2.36 21 521---> echo $var1
1+2+3
$ 4.2.36 22 522--->  var1=1+2,+3
$ 4.2.36 23 523---> echo $var1
1+2 +3
$ 4.2.36 24 524--->

bash -r restricted shell

$ 4.2.36 8 508---> bash -r
$ 4.2.36 1 501---> ls
Algorithms     bookmark  bugs-general  debian-howtos  firewall	kernel	  linux    README
beautifulwork  books	 config-files  Docs	      https:	language  ovlfose
$ 4.2.36 2 502---> cd ..
bash: cd: restricted
$ 4.2.36 3 503---> cd /
bash: cd: restricted
$ 4.2.36 4 504---> ./firewall/firewall.bw
bash: ./firewall/firewall.bw: restricted: cannot specify `/' in command names
$ 4.2.36 5 505---> cat config-files/dot-muttrc > check
bash: check: restricted: cannot redirect output
$ 4.2.36 6 506---> enable
enable .
enable :
enable [
enable alias
enable bg
enable bind
enable break
enable builtin
enable caller
enable cd
enable command
enable compgen
enable complete
enable compopt
enable continue
enable declare
enable dirs
enable disown
enable echo
enable enable
enable eval
enable exec
enable exit
enable export
enable false
enable fc
enable fg
enable getopts
enable hash
enable help
enable history
enable jobs
enable kill
enable let
enable local
enable logout
enable mapfile
enable popd
enable printf
enable pushd
enable pwd
enable read
enable readarray
enable readonly
enable return
enable set
enable shift
enable shopt
enable source
enable suspend
enable test
enable times
enable trap
enable true
enable type
enable typeset
enable ulimit
enable umask
enable unalias
enable unset
enable wait
$ 4.2.36 7 507---> enable
enable .
enable :
enable [
enable alias
enable bg
enable bind
enable break
enable builtin
enable caller
enable cd
enable command
enable compgen
enable complete
enable compopt
enable continue
enable declare
enable dirs
enable disown
enable echo
enable enable
enable eval
enable exec
enable exit
enable export
enable false
enable fc
enable fg
enable getopts
enable hash
enable help
enable history
enable jobs
enable kill
enable let
enable local
enable logout
enable mapfile
enable popd
enable printf
enable pushd
enable pwd
enable read
enable readarray
enable readonly
enable return
enable set
enable shift
enable shopt
enable source
enable suspend
enable test
enable times
enable trap
enable true
enable type
enable typeset
enable ulimit
enable umask
enable unalias
enable unset
enable wait
$ 4.2.36 8 508--->
$ 4.2.36 8 508---> enable --help
bash: enable: --: invalid option
enable: usage: enable [-a] [-dnps] [-f filename] [name ...]
$ 4.2.36 9 509---> enable -d
bash: enable: restricted
$ 4.2.36 10 510--->

reportbug tool

commandline session

$ 4.2.36 8 508---> reportbug --debug
Please enter the name of the package in which you have found a problem, or type 'other' to report a more
general problem.
> testing
*** Welcome to reportbug.  Use ? for help at prompts. ***
Note: bug reports are publicly archived (including the email address of the submitter).
Detected character set: UTF-8
Please change your locale if this is incorrect.

Using 'Jeffrin Jose Thalakkottoor ' as your from address.
Getting status for testing...
No matching source or binary packages.
A package named "testing" does not appear to be installed; do you want to search for a similar-looking filename
in an installed package [Y|n|q|?]? n
Getting available info for testing...
Please enter the version of the package this report applies to (blank OK)
> 1.1
Will send report to Debian (per lsb_release).
Querying Debian BTS for reports on testing (source)...
No bug reports found.

Briefly describe the problem (max. 100 characters allowed). This will be the bug email subject, so keep the
summary as concise as possible, for example: "fails to send email" or "does not start with -q option specified"
(enter Ctrl+c to exit reportbug without reporting a bug).
> testing
How would you rate the severity of this problem or report?

1 critical        makes unrelated software on the system (or the whole system) break, or causes serious data
                  loss, or introduces a security hole on systems where you install the package.
2 grave           makes the package in question unusable by most or all users, or causes data loss, or
                  introduces a security hole allowing access to the accounts of users who use the package.
3 serious         is a severe violation of Debian policy (that is, the problem is a violation of a 'must' or
                  'required' directive); may or may not affect the usability of the package. Note that non-
                  severe policy violations may be 'normal,' 'minor,' or 'wishlist' bugs. (Package maintainers
                  may also designate other bugs as 'serious' and thus release-critical; however, end users
                  should not do so.). For the canonical list of issues worthing a serious severity you can
                  refer to this webpage: http://release.debian.org/wheezy/rc_policy.txt .
4 important       a bug which has a major effect on the usability of a package, without rendering it completely
                  unusable to everyone.
5 does-not-build  a bug that stops the package from being built from source. (This is a 'virtual severity'.)
6 normal          a bug that does not undermine the usability of the whole package; for example, a problem with
                  a particular option or menu item.
7 minor           things like spelling mistakes and other minor cosmetic errors that do not affect the core
                  functionality of the package.
8 wishlist        suggestions and requests for new features.

Please select a severity level: [normal] 7
Do any of the following apply to this report?

1 d-i       This bug is relevant to the development of debian-installer.
2 ipv6      This bug affects support for Internet Protocol version 6.
3 l10n      This bug reports a localization/internationalization issue.
4 lfs       This bug affects support for large files (over 2 gigabytes).
5 patch     You are including a patch to fix this problem.
6 upstream  This bug applies to the upstream part of the package.
7 none

Please select tags: (one at a time) [none]
Spawning sensible-editor...
No changes were made in the editor.
Report will be sent to Jeffrin Jose Thalakkottoor 
Submit this report on testing (e to edit) [y|n|a|c|E|i|l|m|p|q|d|t|s|?]? y
Report is unchanged. Edit this report or quit [E|q|s|?]? s
Sending empty report anyway...
Connecting to smtp.mail.yahoo.com:4100 via SMTP...
SMTP send failure: Connection unexpectedly closed: [Errno 104] Connection reset by peer. Do you want to retry
(or else save the report and exit)? [Y|n|q|?]?

GNU bash –noediting and -v

commandline session

$ 4.2.36 5 505---> bash --noediting
$ 4.2.36 1 501---> tcp
bash: tcp: command not found
$ 4.2.36 2 502--->
$ 4.2.36 2 502---> exit
exit
$ 4.2.36 6 506---> tcprobe

$ 4.2.36 16 516---> bash -v
# System-wide .bashrc file for interactive bash(1) shells.

# To enable the settings / commands in this file for login shells as well,
# this file has to be sourced in /etc/profile.

# If not running interactively, don't do anything
[ -z "$PS1" ] && return

# check the window size after each command and, if necessary,
# update the values of LINES and COLUMNS.
shopt -s checkwinsize

# set variable identifying the chroot you work in (used in the prompt below)
if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then
    debian_chroot=$(cat /etc/debian_chroot)
fi

# set a fancy prompt (non-color, overwrite the one in /etc/profile)
PS1='${debian_chroot:+($debian_chroot)}u@h:w$ '

# Commented out, don't overwrite xterm -T "title" -n "icontitle" by default.
# If this is an xterm set the title to user@host:dir
#case "$TERM" in
#xterm*|rxvt*)
#    PROMPT_COMMAND='echo -ne " 33]0;${USER}@${HOSTNAME}: ${PWD} 07"'
#    ;;
#*)
#    ;;
#esac

# enable bash completion in interactive shells
#if ! shopt -oq posix; then
#  if [ -f /usr/share/bash-completion/bash_completion ]; then
#    . /usr/share/bash-completion/bash_completion
#  elif [ -f /etc/bash_completion ]; then
#    . /etc/bash_completion
#  fi
#fi

# if the command-not-found package is installed, use it
if [ -x /usr/lib/command-not-found -o -x /usr/share/command-not-found/command-not-found ]; then
	function command_not_found_handle {
	        # check because c-n-f could've been removed in the meantime
                if [ -x /usr/lib/command-not-found ]; then
		   /usr/bin/python /usr/lib/command-not-found -- "$1"
                   return $?
                elif [ -x /usr/share/command-not-found/command-not-found ]; then
		   /usr/bin/python /usr/share/command-not-found/command-not-found -- "$1"
                   return $?
		else
		   printf "%s: command not foundn" "$1" >&2
		   return 127
		fi
	}
fi
#export PS1="[ 33[0;31m] $ V # ! "
export PS1="$ V # !---> "

shellp()
{
pre=: post=:
printf "$pre%s$postn" "$@"
}


procmailx ()
{
ORGMAIL=/var/mail/$LOGNAME

if cd $HOME &&
test -s $ORGMAIL &&
lockfile -r0 -l1024 .newmail.lock 2>/dev/null
then
trap "rm -f .newmail.lock" 1 2 3 13 15
umask 077
lockfile -l1024 -ml
cat $ORGMAIL >>.newmail &&
cat /dev/null >$ORGMAIL
lockfile -mu
formail -s procmail

/proc/meminfo related

# cat /proc/meminfo
MemTotal:        1995608 kB
MemFree:           77804 kB
Buffers:          226640 kB
Cached:           306916 kB
SwapCached:         1256 kB
Active:           817952 kB
Inactive:         458696 kB
Active(anon):     553568 kB
Inactive(anon):   193212 kB
Active(file):     264384 kB
Inactive(file):   2100484 kB
Unevictable:        4696 kB
Mlocked:            4696 kB
SwapTotal:       5843964 kB
SwapFree:        5838604 kB
Dirty:               752 kB
Writeback:             0 kB
AnonPages:        746892 kB
Mapped:           132928 kB
Shmem:              1036 kB
Slab:             534784 kB
SReclaimable:     512904 kB
SUnreclaim:        21880 kB
KernelStack:        2688 kB
PageTables:        23316 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     6841768 kB
Committed_AS:    2595056 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      114500 kB
VmallocChunk:   34359621192 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      364480 kB
DirectMap2M:     1667072 kB
#

SHLVL – Incremented by one each time an instance of bash is started

commandline session

$ 4.2.36 2 501---> echo $SHLVL
1
$ 4.2.36 3 502---> echo $SHLVL
1
$ 4.2.36 4 503---> bash
$ 4.2.36 1 500---> echo $SHLVL
2
$ 4.2.36 2 501---> logout
bash: logout: not login shell: use `exit'
$ 4.2.36 3 502---> exit
exit
$ 4.2.36 5 504---> echo $SHLVL
1
$ 4.2.36 6 505--->

BASH_VERSINFO A readonly array variable

commandline session

$ 4.2.36 2 501---> echo BASH_VERSINFO[0]
BASH_VERSINFO[0]
$ 4.2.36 3 502---> echo $BASH_VERSINFO[0]
4[0]
$ 4.2.36 4 503---> echo $BASH_VERSINFO
4
$ 4.2.36 5 504---> echo $BASH_VERSINFO[1]
4[1]
$ 4.2.36 6 505---> echo BASH_VERSINFO[1]
BASH_VERSINFO[1]
$ 4.2.36 7 506---> echo "BASH_VERSINFO[1]"
BASH_VERSINFO[1]
$ 4.2.36 8 507---> echo BASH_VERSINFO(1)
bash: syntax error near unexpected token `('
$ 4.2.36 8 508---> echo BASH_VERSINFO[4]
BASH_VERSINFO[4]
$ 4.2.36 9 509---> echo $BASH_VERSINFO[4]
4[4]
$ 4.2.36 10 510---> echo ?BASH_VERSINFO[4]
?BASH_VERSINFO[4]
$ 4.2.36 11 511---> echo !BASH_VERSINFO[4]
bash: !BASH_VERSINFO[4]: event not found
$ 4.2.36 11 511---> echo ?BASH_VERSINFO[4]
?BASH_VERSINFO[4]
$ 4.2.36 12 512--->