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Functions in Shell Scripting 2
- Thread starter skuthe
- Start date
-
1
- #3
Here are 4 other examples.
Regards,
Ed
1.
# yesorno: This function takes one argument and if the
# value is Y or y returns 1 else it returns 0. Pressing
# <CR> returns 0;
# usage: $(yesorno $answer)
function yesorno {
case $1 in
y|Y) echo 1;;
*)
echo 0;;
esac
} # end yesorno
printf "Answer the question: Y/N: "
read answer
ret_val=$(yesorno $answer)
echo $ret_val
2.
# user_exist: This function takes an argument which is the
# user id, greps the first field of /etc/passwd and sets
# the exit code, 1 if user exists and 0 if not.
# sample the exit code $? from calling program.
function user_exist
{
if grep "^$1:" /etc/passwd > /dev/null 2>&1
then return 1
else return 0
fi
} # end user_exist
Sample the exist code immediately after returning from the user_exist
function:
loginame=alexb
user_exist $loginame
if [ "$?" -eq 0 ]
then printf "User %s does NOT exist\n" $loginame
else printf "User %s exists\n" $loginame
fi
3.
# down_shift: This function takes one argument, downshifts it
# to lowercase, and returns the string
# usage: string=$(down_shift $string)
function down_shift {
local string
string=`echo $1 | tr '[A-Z]' '[a-z]'`
# alternate tr command
#string=`echo $1 | tr "[:upper:]" "[:lower:]"`
echo $string
} # end down_shift
string="ALLLOWERCASE"
string=$(down_shift $string)
echo $string
4.
# is_digit: This function matches an all digits regular expression
# against an argument and returns 1 if the argument is digits else 0
# if isn't.
# Note the use of nawk. Use gawk for the Bash shell.
function is_digit
{
echo $1|nawk ' { if ($0 ~ /^[0-9]+$/)
print 1
else
print 0 } '
} # end is_digit
num="345"
ret_val=$(is_digit $num)
echo $ret_val
Regards,
Ed
1.
# yesorno: This function takes one argument and if the
# value is Y or y returns 1 else it returns 0. Pressing
# <CR> returns 0;
# usage: $(yesorno $answer)
function yesorno {
case $1 in
y|Y) echo 1;;
*)
echo 0;;
esac
} # end yesorno
printf "Answer the question: Y/N: "
read answer
ret_val=$(yesorno $answer)
echo $ret_val
2.
# user_exist: This function takes an argument which is the
# user id, greps the first field of /etc/passwd and sets
# the exit code, 1 if user exists and 0 if not.
# sample the exit code $? from calling program.
function user_exist
{
if grep "^$1:" /etc/passwd > /dev/null 2>&1
then return 1
else return 0
fi
} # end user_exist
Sample the exist code immediately after returning from the user_exist
function:
loginame=alexb
user_exist $loginame
if [ "$?" -eq 0 ]
then printf "User %s does NOT exist\n" $loginame
else printf "User %s exists\n" $loginame
fi
3.
# down_shift: This function takes one argument, downshifts it
# to lowercase, and returns the string
# usage: string=$(down_shift $string)
function down_shift {
local string
string=`echo $1 | tr '[A-Z]' '[a-z]'`
# alternate tr command
#string=`echo $1 | tr "[:upper:]" "[:lower:]"`
echo $string
} # end down_shift
string="ALLLOWERCASE"
string=$(down_shift $string)
echo $string
4.
# is_digit: This function matches an all digits regular expression
# against an argument and returns 1 if the argument is digits else 0
# if isn't.
# Note the use of nawk. Use gawk for the Bash shell.
function is_digit
{
echo $1|nawk ' { if ($0 ~ /^[0-9]+$/)
print 1
else
print 0 } '
} # end is_digit
num="345"
ret_val=$(is_digit $num)
echo $ret_val
-
1
- #5
my exemple, shell-funcs have the same rules as the shell itself: the first 8 argv are remembered in $1 $2 .. $8
$9 remember all other'
#!/bin/sh
printme()
{
while [ $# -ne 0 ]
do echo $1; shift
done
}
printme aa bb cc dd ee ff gg ........ zz vox clamantis in deserto.
$9 remember all other'
#!/bin/sh
printme()
{
while [ $# -ne 0 ]
do echo $1; shift
done
}
printme aa bb cc dd ee ff gg ........ zz vox clamantis in deserto.
Marsd:
Thanks for the kind words. Just for that, here's another example.
This function is a wrapper around tar being used to copy a source
directory to a destination. You need to be careful about passing
strings to a ksh function. This function's argument is a
string with two directories. I use set to break $1 into two
arguments, and I make sure the directories exist before the copy
takes place.
Regards,
Ed
# copy $1 (src) to $2 (destination)
function cp_directory {
set $1 # break $1 argument
if [ ! -d $1 ]
then
return 1 # source doesn't exist
fi
if [ ! -d $2 ]
then
return 1 # destination doesn't exist
fi
cd $1; tar -cf - .|(cd $2; tar -xf - ); return $?
}
cp_directory "/usr/eds/olddir /jet/eds/newdir"
if [ $? -eq 0 ]
then
echo "copy complete"
else
echo "copy failure"
fi
Thanks for the kind words. Just for that, here's another example.
This function is a wrapper around tar being used to copy a source
directory to a destination. You need to be careful about passing
strings to a ksh function. This function's argument is a
string with two directories. I use set to break $1 into two
arguments, and I make sure the directories exist before the copy
takes place.
Regards,
Ed
# copy $1 (src) to $2 (destination)
function cp_directory {
set $1 # break $1 argument
if [ ! -d $1 ]
then
return 1 # source doesn't exist
fi
if [ ! -d $2 ]
then
return 1 # destination doesn't exist
fi
cd $1; tar -cf - .|(cd $2; tar -xf - ); return $?
}
cp_directory "/usr/eds/olddir /jet/eds/newdir"
if [ $? -eq 0 ]
then
echo "copy complete"
else
echo "copy failure"
fi
olded: dangerous
suppose: cp_directory /usr/eds/olddir /usr/eds/olddir.
you don't need to split $1 if you pass args NOT quoted.
my i propose: tar cfb - 126k . |(cd $2;tar xfp -)
in a previous example:
if [ "$?" -eq 0 ] #numerical comp of a string??
why disturb
?awk to do this ????
function is_digit
{
case x$1 in x[0-9]*[0-9]) return 1;; esac
return 0
} # end is_digit
vox clamantis in deserto.
suppose: cp_directory /usr/eds/olddir /usr/eds/olddir.
you don't need to split $1 if you pass args NOT quoted.
my i propose: tar cfb - 126k . |(cd $2;tar xfp -)
in a previous example:
if [ "$?" -eq 0 ] #numerical comp of a string??
why disturb
?awk to do this ????function is_digit
{
case x$1 in x[0-9]*[0-9]) return 1;; esac
return 0
} # end is_digit
vox clamantis in deserto.
If I can't use awk, can I use expr?
# return 1 if argument is numeric else 0
function is_digit {
if [ $# -ne 1 ]
then
echo 0
fi
expr "$1" + 1 > /dev/null 2>&1
if [ $? -eq 0 ]
then
echo 1
else
echo 0
fi
}
num="345"
ret_val=$(is_digit $num)
echo $ret_val
# return 1 if argument is numeric else 0
function is_digit {
if [ $# -ne 1 ]
then
echo 0
fi
expr "$1" + 1 > /dev/null 2>&1
if [ $? -eq 0 ]
then
echo 1
else
echo 0
fi
}
num="345"
ret_val=$(is_digit $num)
echo $ret_val
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