Shell – if/then/else man page

documentationmanscriptingshell

I would like to know if there is any man page documenting the construction of the most basic script commands like if/then/else, while, for each, and all the relative switches, like -eq, -e, -ge, and so on.

Best Answer

You have to look at the manual for the specific shell you are using as the exact syntax for using these constructs can vary between shells. Most likely you are using bash, so you would do man bash. Although there are many cases where you might be using something else. For example many distros use a POSIX shell for boot scripts (eg Debian uses dash) or a least use bash in POSIX compliant mode. Usually you can do man sh to get the documentation in this case (this will be linked to the man page for the shell used if it is not the original sh or Bourne shell).

If you are unsure which shell you are using, see this question - determine shell in script during runtime

Another thing work mentioning is the help builtin for bash, it gives an abbreviated version of what is in the manual for the various builtin commands/flow control statements etc. You can use help on its own to see a full list of what is available, otherwise you can try things like help if, help for, help test and help [.

Related Solutions

Linux Man Page – Open and Search for String in One Command

Try this trick:

man chmod | less +'/a\+x'

man chmod | more +'/a\+x'

With a backslash before the + sign because what comes after / is an extended regular expression.

Any way to cat few lines of man page to show on stdout for reference

You could run the output of man into the col command and then pipe this to less. Once in less you can drop to a shell while still maintaining your location in less.

$ man col | col -b | less

Once in less you can use !bash to get to a prompt to do what you want. When you're done you type exit to return back to your location in less.

Example

Here's a demo showing the whole operation.

ss of demo

Tell man to use a different pager

You can also tell man to use different pagers via the -P switch. So we could streamline the above method like so:

$ man -P less col

This is invoking man and then outputting the contents of the page to less, where again we can use !bash to get to a shell. To return we use the same steps as above, exit.

What's wrong with the default pager?

Actually nothing.

$ man col

It too can take the command !bash to escape to a shell, where again we can type exit to get back to the location where we were previously within the man page.

What else?

If you're feeling really crazy you can use vim as an alternative pager too. Setting this up is a bit of a task but it's doable, directions for doing so are here in the vim wikia topic titled: Using vim as a man-page viewer under Unix.

Don't let the above page fool you, it doesn't just cover vim methods. That topic covers dozens of ways you can change your man page pager in addition to using vim.