Helpful Unix commands - Part 2

- When shell script complains of ^M character which is a windows character
sh: /opt/tmp/testPerson.sh: /usr/bin/ksh^M: bad interpreter: No such file or directory

Reason is there may be DOS linefeeds in your file. Convert the file to Unix linefeeds, either by copying the file using ASCII mode FTP, or one of:

tr -d '\r' < script > script.new

perl -pi -e 's/\r$//;' script

dos2unix < script > script.new



-To Change permissions
chmod 775 <>
chmod -R 775 <> [for recursive]


-To Move Files from One server to another
scp username@servername:/opt/tmp/filename filename


To connect to B server from A server
From A server type
ssh username@serverB


-To check if a directory exist

if [ -d mydir ]
then
echo "Directory found"
else
echo "Directory not found"
fi


-To check if a file exists

#(-f === if file exists)
if test -f $TMP;
then
if test ! -w $TMP ;
then
printf the temp file $TMP exists and cannot be overwritten aborting >&2
exit 192
fi
fi


- To copy a file
cp -p <> <>
- To copy a directory
cp -p -R <> <>

- To remove a file
rm <>
- To remove a directory
rm -d -R <,filename>>


- To find out if perl or bash or sh file exists
which perl
which bash
which sh


- To find out the version of linux
cat /etc/redhat-release

- To change group name of a file
chgrp <> <>