Unix: print in color

This simple procedure takes 3 arguments as the parameters:

  • Text
  • Foreground color
  • Background color

It prints the text to the terminal in selected colors.

[cc lang=”bash”]
function print_color {
local text=$1
local fg=$2
local bg=$3
case “$fg” in
red) fg=”31m” ;;
green) fg=”32m” ;;
yellow) fg=”33m” ;;
blue) fg=”34m” ;;
white) fg=”37m” ;;
black) fg=”30m” ;;
*) fg=”37m” ;;
case “$bg” in
red) bg=”41m” ;;
green) bg=”42m” ;;
yellow) bg=”43m” ;;
blue) bg=”44m” ;;
white) bg=”47m” ;;
black) bg=”40m” ;;
*) bg=”40m” ;;
echo -en “\033[${fg}\033[${bg}${text}\033[0m”

Unix: rename files to lowercase

It’s very simple to rename the files to lowercase/uppercase using awk:

[cc lang=”bash”]
ls -1rt | awk ‘{ printf(“mv %s %s\n”, $0, tolower($0)) | “sh” } END { close(“sh”) }’

[cc lang=”bash”]
ls -1rt | awk ‘{ printf(“mv %s %s\n”, $0, toupper($0)) | “sh” } END { close(“sh”) }’

Reading password in Unix shell

print -n "Enter Your password:"
stty_orig=`stty -g`
trap "stty ${stty_orig}; exit" 1 2 3 15
stty -echo >&- 2>&-
read PASS
stty ${stty_orig} >&- 2>&-
trap 1 2 3 15

trap :catches interruptions. I.e. if the user presses Ctrl+C, the normal stty mode is set before stopping the program
stty -echo :switches off the display echo
>&- 2>&- :helps to avoid “stty: Not a typewriter” message for non-interactive scripts.

Unix shell: workaround for loop problem

It’s not possible to get the value of the loop variables in some versions of ksh.



cat $0 | while read line ; do
let num=num+1

echo "Number=$num"

This script will return “Number=0” as the result on some Linux machines.

Here is the workaround for the problem: You should change the redirection method for the input file.


while read line ; do
let l=l+1
done < $0 echo "Number=$l"

The last script will return the correct result: "Number=9"

Another possibility is to use the named pipe:


mkfifo $TMPPIPE
cat $0 > $TMPPIPE &
while read line ; do
let num=num+1
done < $TMPPIPE echo "Number=$num"

Using pattern lists in Unix

Here is the small reminder about the syntax of the “case” command and the usage of the pattern lists.

print -n "Please enter the line: "
read line

case "$line" in
?(dog|cat) ) print "zero or one occurrence of any pattern" ;;
*(low|high) ) print "zero or more occurrences of any pattern" ;;
@(duncan|methos) ) print "exactly one occurrence of any pattern" ;;
+(rudolph|blitzen) ) print "one or more occurrence of any pattern" ;;
!(grinch|babay) ) print "everything except patterns" ;;
-@([hH?]) ) print "Some help..." ;;
-v*(erbose) ) print "Some more words..." ;;
*) print "Something else..." ;;

Print the PATH directories in the readable format

echo $PATH| awk -v RS=":" '{ print $0 }'

echo $LD_LIBRARY_PATH |awk -v RS=":" '{ system ( "ls -rltd " $0 ) }'

As far as the option ‘-v’ is used, the new awk(nawk in some systems) should be used.

To check if the new version of awk is installed:

awk 1 /dev/null

The output will be empty for new awk.
You have the old awk, if the output is something like

awk: syntax error near line 1

In this case nawk should be used instead awk

MS-DOS modification: echo %PATH% | awk -v RS=”;” “{ print $0 }”