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File Handling using Shell Scripts

File handling using Shell Scripts

  1. to prepend a line to a file
  2. to develop a temporary file name generator
  3. to compare two files


    Suse Linux, BASH Scripting


(a) Prepending a line to a file



# Add text at beginning of file.




read -p "File: " file   # -p arg to 'read' displays prompt.

if [ ! -e "$file" ]

    then   # Bail out if no such file.

    echo "File $file not found."

    exit $E_NOSUCHFILE



read -p "Title: " title

cat - $file <<<$title > $

echo "Modified file is $"

exit 0


(b) to develop a temporary file name generator


#  temp filename generator

BASE_STR=`mcookie`   # 32-character magic cookie.

POS=11               # Arbitrary position in magic cookie string.

LEN=5                # Get $LEN consecutive characters.

prefix=temp          #  This is, after all, a "temp" file.

#  For more "uniqueness," generate the filename prefix

#+ using the same method as the suffix, below.



# Extract a 5-character string, starting at position 11.


# Construct the filename.

echo "Temp filename = "$temp_filename""

# sh

# Temp filename = temp.e19ea

exit 0


(c) Comparing two files


ARGS=2  # Two args to script expected.



if [ $# -ne "$ARGS" ]


  echo "Usage: `basename $0` file1 file2"

  exit $E_BADARGS



if [[ ! -r "$1" || ! -r "$2" ]]


  echo "Both files to be compared must exist and be readable."




cmp $1 $2 &> /dev/null  # /dev/null buries the output of the "cmp" command.

if [ $? -eq 0 ]         # Test exit status of "cmp" command.


  echo "File \"$1\" is identical to file \"$2\"."


  echo "File \"$1\" differs from file \"$2\"."


exit 0




Open the VI editor

$: vi <filename>

Compile using bash

$: sh <filename>


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