Ubuntu – put a user-defined shell function

bashcommand linefunctions

I am planning to create a function that would simplify things for me. The function would be something like

function lazymode()
{
echo "Hello World!";
}

so that when I use the command lazymode in the shell , it will output the Hello World!.

What file should I put the user-defined function?

Best Answer

Depends on the function. If it's just a super-simple one-liner like that you could create an alias or stick the function in ~/.bashrc (a file that bash loads when it starts).

If you're creating something a bit more meaty, it might make more sense to create its own executable script in ~/bin/ which won't exist by default (it's just a directory) but should be in your path. Remember for this the file will need to be executable (chmod +x filename) and start with a proper #!/bin/bash stanza.

The second route has some clear benefits:

It's easier to see what's available
A syntax error won't tank your profile
You don't need to keep re-sourcing your bash config if you change the script
It's available to any shell as long as the full path is used or ~/bin/ is in the path for that shell too (which it should be in most cases AFAIK).

Related Solutions

Understanding Shell Quoting in Bash

I've tried to break this down a little bit for you, using your own examples/text as well, check it out:

$ cat fred    
#!/bin/bash

fred='Four spaces between these    words.'

echo "The value of \$fred is $fred"

echo "The next line being printed is simply the results of # echo \$fred"

echo $fred

Running the bash script above prints the following to the terminal/stdout:

The value of $fred is Four spaces between these    words.
The next line being printed is simply the results of # echo $fred
Four spaces between these words.

As well, you can view a terminal video of this here: http://showterm.io/98f56243f60551b338b9f

How to Remove Text Using Sed Command in Linux

To reverse the effect of your command AND keeping the same part of the string to be matched (assuming that this is the only fix part of the string and you want to get rid of any other part that may vary), you can do :

echo "hello world, I am just simple text for display." | sed 's/^.*\(, I am.*\)/\1/g'

Result :

, I am just simple text for display

What the regular expression is doing :

^.* : matching any character at the beginning of the string until the next expression
\( & \) : to catch the part of the string which is matched by the expression in between (must be escaped by \ or they will match the parenthesis character).
, I am.* : the match you give us,
\1 : will be replaced by the result of the match of the first sub-expression between parenthesis

This way, you have the exact reverse effect of the command in your question, using the same part of the string to do the match.

Best Answer

Related Solutions

Understanding Shell Quoting in Bash

How to Remove Text Using Sed Command in Linux

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