今天無(wú)意中發(fā)現(xiàn)一本挺有意思的shell編程的書，是e文的，內(nèi)容是101個(gè)shell案例，堅(jiān)持明天看一個(gè)，寫點(diǎn)心得。
下面是例子001：
#!/bin/sh
# inpath - Verifies that a specified program is either valid as is,
# or that it can be found in the PATH directory list.
in_path()
{
# Given a command and the PATH, try to find the command. Returns
# 0 if found and executable, 1 if not. Note that this temporarily modifies
# the IFS (input field separator) but restores it upon completion.
cmd=$1 path=$2 retval=1
oldIFS=$IFS IFS=":"
for directory in $path
do
if [ -x $directory/$cmd ] ; then
retval=0 # if we're here, we found $cmd in $directory
fi
done
IFS=$oldIFS
return $retval
}
checkForCmdInPath()
{
var=$1
# The variable slicing notation in the following conditional
# needs some explanation: ${var#expr} returns everything after
# the match for 'expr' in the variable value (if any), and
# ${var%expr} returns everything that doesn't match (in this
# case, just the very first character. You can also do this in
# Bash with ${var:0:1}, and you could use cut too: cut -c1.
if [ "$var" != "" ] ; then
if [ "${var%${var#?}}" = "/" ] ; then
if [ ! -x $var ] ; then
return 1
fi
elif ! in_path $var $PATH ; then
return 2
fi
fi
}
if [ $# -ne 1 ] ; then
echo "Usage: $0 command" >2 ; exit 1
fi
checkForCmdInPath "$1"
case $? in
0 ) echo "$1 found in PATH" ;;
1 ) echo "$1 not found or not executable" ;;
2 ) echo "$1 not found in PATH" ;;
esac
exit 0
