sed command – nixCraft

Sample sed code to remove all comments from sed

#! /bin/sed -nf

# Remove C and C++ comments, by Brian Hiles (brian_hiles@rocketmail.com)

# Sped up (and bugfixed to some extent) by Paolo Bonzini (bonzini@gnu.org)
# Works its way through the line, copying to hold space the text up to the
# first special character (/, ", ').  The original version went exactly a
# character at a time, hence the greater speed of this one.  But the concept
# and especially the trick of building the line in hold space are entirely
# merit of Brian.

:loop

# This line is sufficient to remove C++ comments!
/^\/\// s,.*,,

/^$/{
  x
  p
  n
  b loop
}
/^"/{
  :double
  /^$/{
    x
    p
    n
    /^"/b break
    b double
  }

  H
  x
  s,\n\(.[^\"]*\).*,\1,
  x
  s,.[^\"]*,,
  
  /^"/b break
  /^\\/{
    H
    x
    s,\n\(.\).*,\1,
    x
    s/.//
  }
  b double
}

/^'/{
  :single
  /^$/{
    x
    p
    n
    /^'/b break
    b single
  }
  H
  x
  s,\n\(.[^\']*\).*,\1,
  x
  s,.[^\']*,,
  
  /^'/b break
  /^\\/{
    H
    x
    s,\n\(.\).*,\1,
    x
    s/.//
  }
  b single
}

/^\/\*/{
  s/.//
  :ccom
  s,^.[^*]*,,
  /^$/ n
  /^\*\//{
    s/..//
    b loop
  }
  b ccom
}

:break
H
x
s,\n\(.[^"'/]*\).*,\1,
x
s/.[^"'/]*//
b loop

#! /bin/sed -nf

# Remove C and C++ comments, by Brian Hiles (brian_hiles@rocketmail.com)

# Sped up (and bugfixed to some extent) by Paolo Bonzini (bonzini@gnu.org)

# Works its way through the line, copying to hold space the text up to the

# first special character (/, ", '). The original version went exactly a

# character at a time, hence the greater speed of this one. But the concept

# and especially the trick of building the line in hold space are entirely

# merit of Brian.

:loop

# This line is sufficient to remove C++ comments!

/^\/\// s,.*,,

/^$/{

b loop

}

/^"/{

:double

/^$/{

/^"/b break

b double

}

s,\n$.[^\"]*$.*,\1,

s,.[^\"]*,,

/^"/b break

/^\\/{

s,\n$.$.*,\1,

s/.//

}

b double

}

/^'/{

:single

/^$/{

/^'/b break

b single

}

s,\n$.[^\']*$.*,\1,

s,.[^\']*,,

/^'/b break

/^\\/{

s,\n$.$.*,\1,

s/.//

}

b single

}

/^\/\*/{

s/.//

:ccom

s,^.[^*]*,,

/^$/ n

/^\*\//{

s/..//

b loop

}

b ccom

}

:break

s,\n$.[^"'/]*$.*,\1,

s/.[^"'/]*//

b loop

Please note that this program is copied from public domain.

This script uses sed command to find out all digits or upper characters. -z string (conditional expression) will return true if the length of string is zero.

Script logic

Read one character
[1] Use sed command to determine input character is digit or not (sed -e ‘s/[A-Z]//g’))

[2] Attempt to match regex [0-9] i.e. all digit against the pattern space

[3] If successful, replace that portion matched with replacement // i.e. do nothing.
If digits are in input, it will replace all those digit, and if input is only digit, nothing is left i.e. string is zero and that is what tasted with -z conditional expression.

#!/bin/bash
# Shell script to read a character (upper or lower), digit, special symbol and
# display message according to the character entered
# -----------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------

char=""
echo -n "Enter a one character : "
read char
# use sed command to determine input character is digit or not
# -e : start script
# s/[0-9]// : Attempt to match regex [0-9] i.e. all digit against the pattern space (echo $char).
# If  successful,  replace  that  portion  matched  with replacement i.e. // do nothing. 
# g : Global replacement
# so if digit are in input it will replace all those digit, and if input is only digit, nothing
# is left i.e. string is zero and that is what tasted with -z
if [ -z $(echo $char | sed -e 's/[0-9]//g') ]
then
	echo "$char is Number/digit"
elif [ -z $(echo $char | sed  -e 's/[A-Z]//g') ] # find out if character is upper
then
        echo "$char is UPPER character"

elif [ -z $(echo $char | sed -e 's/[a-z]//g') ] # find out if character is lower
then
        echo "$char is lower character"
else
	echo "$char is Special symbol" # else it is special character
fi

#!/bin/bash

# Shell script to read a character (upper or lower), digit, special symbol and

# display message according to the character entered

# -----------------------------------------------

# This script is licensed under GNU GPL version 2.0 or above

# -------------------------------------------------------------------------

# This script is part of nixCraft shell script collection (NSSC)

# Visit http://bash.cyberciti.biz/ for more information.

# -------------------------------------------------------------------------

char=""

echo -n "Enter a one character : "

read char

# use sed command to determine input character is digit or not

# -e : start script

# s/[0-9]// : Attempt to match regex [0-9] i.e. all digit against the pattern space (echo $char).

# If successful, replace that portion matched with replacement i.e. // do nothing.

# g : Global replacement

# so if digit are in input it will replace all those digit, and if input is only digit, nothing

# is left i.e. string is zero and that is what tasted with -z

if [ -z $(echo $char | sed -e 's/[0-9]//g') ]

then

echo "$char is Number/digit"

elif [ -z $(echo $char | sed -e 's/[A-Z]//g') ] # find out if character is upper

then

echo "$char is UPPER character"

elif [ -z $(echo $char | sed -e 's/[a-z]//g') ] # find out if character is lower

then

echo "$char is lower character"

else

echo "$char is Special symbol" # else it is special character

nixCraft

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Tag: sed command

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How do I use this sed script?

Sample sed code to remove all comments from sed

Shell script to read a character (upper or lower), digit, special symbol and display message according to the character entered

Script logic