environ -- user environment

strings called the environment of the form name=value.

COLUMNS width in column positions for the terminal. Used by various utilities.
If unset or empty, some utilities will use an ioctl call to ask the terminal driver.
This is adjusted by some terminal emulators ( including ssh) if the window is re-sized.
Can also be changed with the ANSI terminal control sequences. For example:
echo $'\e[8;38;140t'
BLOCKSIZE used by df, du, ls and others. specified in units of byte by specifying a number, kilobyte using K or k, megabyte M or m and gigabyte G or g.
EXINIT startup commands read by editors
HOME user's login directory, set by login from /etc/passwd.
PATH sequence of directories searched by shells, system(3), execvp(3), etc, when looking for executables .
PRINTER default printer
SHELL full pathname of the user's login shell.
TERM type of terminal in use /usr/share/misc/termcap (TERMCAP)
TERMCAP string describing the capabilities of terminal in TERM or the name of the termcap file.
TERMPATH pathnames for termcap files, searched for terminal capabilities. Defaults to $HOME/.termcap:/etc/termcap, ignored if TERMCAP is a full pathname.
TMPDIR directory for temporary files. Defaults to /tmp or /var/tmp. These may be deleted at system startup.
TZ timezone to use when displaying dates. The normal format is a pathname relative to /usr/share/zoneinfo. For example, the command env TZ=US/Pacific date displays the current time in California. See tzset(3) for more information.
LOGNAME login name of the user.
USER Deprecated synonym of LOGNAME (for backwards compatibility).

related to a particular locale as displayed by locale
(example monetary denomination dollars, pounds, yen... date format mm-dd-yy , dd-mm-yy).
LANG=
LC_ALL
LC_CTYPE="POSIX"
LC_NUMERIC="POSIX"
LC_TIME="POSIX"
LC_COLLATE="POSIX"
LC_MONETARY="POSIX"
LC_MESSAGES="POSIX"
LC_PAPER="POSIX"
LC_NAME="POSIX"
LC_ADDRESS="POSIX"
LC_TELEPHONE="POSIX"
LC_MEASUREMENT="POSIX"
LC_IDENTIFICATION="POSIX"

The author of any script or command can define which names in the environment are used.

Additional entries are placed in the environment with export and name=value arguments in sh, or by the setenv command in csh.
Following is the environment for a CGI script on this host
BASH=/bin/sh
BASH_VERSINFO=([0]="2" [1]="05b" [2]="0" [3]="1" [4]="release" 
               [5]="i386-redhat-linux-gnu")
BASH_VERSION='2.05b.0(1)-release'
DIRSTACK=()
DOCUMENT_ROOT=/home/real1/public_html
EUID=32284
GATEWAY_INTERFACE=CGI/1.1
GROUPS=()
HOSTNAME=esc45.midphase.com
HOSTTYPE=i386
HTTP_ACCEPT='text/xml,application/xml,application/xhtml+xml,
            text/html;q=0.9,text/plain;q=0.8,
            image/png,*/*;q=0.5'
HTTP_ACCEPT_ENCODING='gzip, deflate'
HTTP_ACCEPT_LANGUAGE=en-us
HTTP_CONNECTION=keep-alive
HTTP_COOKIE='C=54; L=1121725408; U=1194191939'
HTTP_HOST=www.tems.com
HTTP_USER_AGENT='Mozilla/5.0 (Macintosh; U; PPC Mac OS X; en-us) 
         AppleWebKit/523.10.6 (KHTML, like Gecko) Version/3.0.4 
          Safari/523.10.6'
IFS='   
'
MACHTYPE=i386-redhat-linux-gnu
OPTERR=1
OPTIND=1
OSTYPE=linux-gnu
PATH=/usr/local/bin:/usr/bin:/bin
PIPESTATUS=([0]="0")
POSIXLY_CORRECT=y
PPID=2141
PS4='+ '
PWD=/home/real1/public_html
QUERY_STRING=
REDIRECT_STATUS=500
REDIRECT_URL=/birding/log/birdlogert.cgi
REMOTE_ADDR=9.25.15.11
REMOTE_PORT=50178
REQUEST_METHOD=GET
REQUEST_URI=/birding/log/birdlogert.cgi
SCRIPT_FILENAME=/home/rear1/public_html/500.cgi
SCRIPT_NAME=/500.cgi
SERVER_ADDR=26.14.34.54
SERVER_ADMIN=web@tems.com
SERVER_NAME=www.tems.com
SERVER_PORT=80
SERVER_PROTOCOL=HTTP/1.1
SERVER_SOFTWARE='Apache/1.3.37 (Unix) 
                 mod_auth_passthrough/1.8 mod_log_bytes/ 1.2 
                 mod_bwlimited/1.4 PHP/4.4.4 
                 FrontPage/5.0.2.2635.SR1.2 mod_ssl/ 2.8.28 
                 OpenSSL/0.9.7a'
SHELL=/usr/local/cpanel/bin/jailshell
SHELLOPTS=braceexpand:hashall:interactive-comments:posix
SHLVL=1
TERM=dumb
UID=32284
_='+%m/%d %H:%M:%S '
Environment on the same host as a terminal
BASH=/usr/local/cpanel/bin/jailshell
BASH_VERSINFO=([0]="2" [1]="05b" [2]="0" [3]="1" [4]="release" 
              [5]="i386-redhat-linux-gnu")
BASH_VERSION='2.05b.0(1)-release'
CLASSPATH=.:/usr/local/jdk/lib/classes.zip
COLORS=/etc/DIR_COLORS
COLUMNS=110
DIRSTACK=()
DNS=tems.com
EDITOR=vi
EUID=32284
EXINIT='set showmode ignorecase ruler tabstop=4 mesg verbose exrc'
GREP_COLOR=red
GROUPS=()
G_BROKEN_FILENAMES=1
HISTFILE=/home/real1/.bash_history
HISTFILESIZE=1000
HISTSIZE=1000
HOME=/home/real1
HOSTNAME=esc4.se.com
HOSTTYPE=i386
HTML=/home/user/mar/public_html
IFS=$' \t\n
INPUTRC=/etc/inputrc
JAVA_HOME=/usr/local/jdk
LANGVAR=
LESS='-X  --LONG-PROMPT -P file\:%f\ %Pb\%\ \ \ help,forward,back,quit, / (srch)'
LESSOPEN='|/usr/bin/lesspipe.sh %s'
LINES=32
LOGNAME=real1
LS_COLORS='no=00:fi=00:di=01;34:ln=01;36:pi=40;33:so=01;35:do=01;35:bd=40;33;01:
           cd=40;33;01:or=40;31;01:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arj=01;31:
           *.taz=01;31:*.lzh=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.gz=01;31:
           *.bz2=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.jpg=01;35:
           *.jpeg=01;35: *.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:
           *.ppm=01;35:*.tga=01;35: *.xbm=01;35:*.xpm=01;35:*.tif=01;35:
           *.tiff=01;35:*.png=01;35:*.mpg=01;35: *.mpeg=01;35:*.avi=01;35:
           *.fli=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.ogg=01;35:
           *.mp3=01;35:*.wav=01;35:'
LS_OPTIONS='--color=tty -F -a -b -T 0'
MACHTYPE=i386-redhat-linux-gnu
MAIL=/var/spool/mail/realger1
MAILCHECK=60
MANPATH=/usr/lib/courier-imap/man:
OLDPWD=/home/realger1/www
OPTERR=1
OPTIND=1
OSTYPE=linux-gnu
PAGER=less
PATH=/home/real1/.bin:/usr/local/jdk/bin:/usr/kerberos/bin:/usr/lib/courier-imap/bin:
     /usr/local/bin:/bin:/usr/bin:/usr/X11R6/bin:/usr/local/bin:/usr/X11R6/bin:
     /usr/libexec:/home/real1/bin
PIPESTATUS=([0]="0")
PPID=25032
PS1='$PWD > '
PS2='> '
PS4='+ '
PWD=/home/real1/www/docs
RWS=Real-World-Systems.com
SHELL=/usr/local/cpanel/bin/jailshell
SHELLOPTS=braceexpand:hashall:histexpand:interactive-comments:monitor:vi
SHLVL=1
SSH_CLIENT='9.2.15.11 50978 22'
SSH_CONNECTION='9.2.15.11 50978 26.14.4.5 22'
SSH_TTY=/dev/pts/0
TERM=xterm-color
TZ=US/Eastern
UID=32284
USER=realger1
VISUAL=pico
_=environ.7.html
today='Jan 18'
whoami=real1
x=28
SEE bash csh ex login sh execve execle system termcap termcap.5

tcsh(1), exec(3) clearenv(3), getenv(3), putenv(3), setenv(3), unsetenv(3) locale