Overwrite .bash_profile file in linux

Question

in my .bash_profile file i want to update value of PATH variable. Also, want to add JAVA_PATH and JRE_HOME variables. And, I want to do all this with Shell Script .

I have no idea about how to do this with commands, so I overwrite the entire file using cat command-

cat >> ~/.bash_profile << _EOF_
#!/bin/bash/
if [ -f ~/.bashrc ]; then
.~/.bashrc
fi

#User specific environment and startup programs
JAVA_PATH=/usr/java/jdk1.6.0_35/bin
PATH=$JAVA_PATH:$PATH:HOME/bin
JRE_HOME=/usr/jdk1.6.0_35

export PATH
unset USERNAME
_EOF_

What would be the impact of doing so with this file? How i can easily update value of PATH variable and insert JAVA_PATH and JRE_HOME variables in this file?

Answer 1

You need to use some text manipulation tool - like sed or awk...

Here is simple example of how to change the PATH value in your .bash_profile

sed 's/^\([[:space:]]*PATH=\)\(.*\)$/\1"\/bin:\/usr\/bin:~\/bin"/' ~/.bash_profile

Notice the escaped special characters ( and /

It you want to overwrite your old file, you need to do it through temporary file like:

sed ... > /tmp/tmpbashprofile$$
mv /tmp/tmpbashprofile$$ ~/.bash_profile

Adding new settings is easy:

echo "JAVA_PATH=/usr/java/jdk1.6.0_35/bin" >> ~/.bash_profile

Notice the double >> - it appends data to specified file