Drush installation - setting symlink to /usr/local/bin/drush is a must? Refering to https://www.drupal.org/node/2132447, I would like to install Drush in /usr/slocal/abc directory, and I tried the following steps:

$ cd /usr/slocal/abc
$ wget --quiet -O - http://ftp.drupal.org/files/projects/drush-7.x-5.9.tar.gz
$ tar -zxf drush-7.x-5.9.tar.gz
$ ln -s /usr/slocal/abc/drush/drush /usr/local/bin/drush


Then, I got this error:


  ln: creating symbolic link '/usr/local/bin/drush': Permission denied


I asked my system admin who said that the company policy does not allow to install stuff into /usr/local/bin. 

I've searched many installation guides, all of them requires to create a symbolic link '/usr/local/bin/drush' in order to run Drush. Is there any other way I can do it?
This may not answer the question directly, but a preferred and much simpler way to install Drush, is to install it through the Composer.

Installing Composer

See Composer's website for greater detail.

curl -sS https://getcomposer.org/installer | php
# If the above code fails, use this one.
# php -r "readfile('https://getcomposer.org/installer');" | php
sed -i '1i export PATH="$HOME/.composer/vendor/bin:$PATH"' $HOME/.bashrc source $HOME/.bashrc


Installing Drush

See Drush instructions on GitHub for greater detail.

To install Drush 6:

composer global require drush/drush:6.*


Or to install Drush 7:

composer global require drush/drush:dev-master


Update

Per @leekit, he was able to solve his original issue by substituting the symbolic link with export PATH="$PATH:/path/to/drush:/usr/local/bin". For that and other alternatives, refer to step 3 of Install - Manual, on Drush instructions on GitHub.