explaination of shell script required
Posted: Tue Apr 13, 2004 4:10 am
i'm new to linux .so please explain this following shell script.
Code: Select all
#! /bin/sh
# Guess values for system-dependent variables and create
## --------------------- ##
## M4sh Initialization. ##
## --------------------- ##
# Be Bourne compatible
if test -n "${ZSH_VERSION+set}" && (emulate sh) >/dev/null 2>&1; then
emulate sh
NULLCMD=:
# Zsh 3.x and 4.x performs word splitting on ${1+"$@"}, which
# is contrary to our usage. Disable this feature.
alias -g '${1+"$@"}'='"$@"'
elif test -n "${BASH_VERSION+set}" && (set -o posix) >/dev/null 2>&1; then
set -o posix
fi
DUALCASE=1; export DUALCASE # for MKS sh
# Support unset when possible.
if ( (MAIL=60; unset MAIL) || exit) >/dev/null 2>&1; then
as_unset=unset
else
as_unset=false
fi
# Work around bugs in pre-3.0 UWIN ksh.
$as_unset ENV MAIL MAILPATH
PS1='$ '
PS2='> '
PS4='+ '
# NLS nuisances.
for as_var in \
LANG LANGUAGE LC_ADDRESS LC_ALL LC_COLLATE LC_CTYPE LC_IDENTIFICATION \
LC_MEASUREMENT LC_MESSAGES LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER \
LC_TELEPHONE LC_TIME
do
if (set +x; test -z "`(eval $as_var=C; export $as_var) 2>&1`"); then
eval $as_var=C; export $as_var
else
$as_unset $as_var
fi
done
# Required to use basename.
if expr a : '\(a\)' >/dev/null 2>&1; then
as_expr=expr
else
as_expr=false
fi
if (basename /) >/dev/null 2>&1 && test "X`basename / 2>&1`" = "X/"; then
as_basename=basename
else
as_basename=false
fi
# Name of the executable.
as_me=`$as_basename "$0" ||
$as_expr X/"$0" : '.*/\([^/][^/]*\)/*$' \| \
X"$0" : 'X\(//\)$' \| \
X"$0" : 'X\(/\)$' \| \
. : '\(.\)' 2>/dev/null ||
echo X/"$0" |
sed '/^.*\/\([^/][^/]*\)\/*$/{ s//\1/; q; }
/^X\/\(\/\/\)$/{ s//\1/; q; }
/^X\/\(\/\).*/{ s//\1/; q; }
s/.*/./; q'`