Command Detail - E

echo

echo is an alias in PowerShell. As you would expect it's an alias for the closest equivalent to the Linux echo:

• write-output

You use it as follows:

write-output "Blue is the colour"

As well as write-output there are a couple of options for use in Powershell scripts and functions:

• write-debug

• write-verbose

Whether these produce any output is controlled by commandline or environment flags.

echo -n

In bash, echo -n echoes back the string without printing a newline, so if you do this:

$ echo -n Blue is the colour

you get:

Blue is the colour$

....with your cursor ending up on the same line as the output, just after the dollar prompt

Powershell has an exact equivalent of 'echo -n'. If you type:

PS C:\Users\matt> write-host -nonewline "Blue is the colour"

....then you get this:

PS C:\Users\matt> write-host -nonewline "Blue is the colour"
Blue is the colourPS C:\Users\matt>

Note that -nonewline doesn't 'work' if you're in the ISE.

egrep

The best PowerShell equivalent to egrep or grep is select-string:

select-string stamford blue_flag.txt

A nice feature of select-string which isn't available in grep is the -context option. The -context switch allows you to see a specified number of lines either side of the matching one. I think this is similar to SEARCH /WINDOW option in DCL.

egrep -i

Powershell is case-insensitive by default, so:

select-string stamford blue_flag.txt

...would return:

blue_flag.txt:3:From Stamford Bridge to Wembley

If you want to do a case sensitive search, then you can use:

select-string  -casesensitive stamford blue_flag.txt

egrep -v

The Powershell equivalent to the -v option would be -notmatch

select-string -notmatch stamford blue_flag.txt

egrep 'this|that'

To search for more than one string within a file in bash, you use the syntax:

egrep 'blue|stamford' blue_flag.txt

This will return lines which contain either 'blue' or 'stamford'.

The PowerShell equivalent is to seperate the two strings with a comma, so:

$ select-string  stamford,blue blue_flag.txt

...returns:

blue_flag.txt:2:We'll keep the blue flag flying high
blue_flag.txt:3:From Stamford Bridge to Wembley
blue_flag.txt:4:We'll keep the blue flag flying high

| egrep -i sql

This is an interesting one, in that it points up a conceptual difference between PowerShell and Bash.

In bash, if you want to pipe into a grep, you would do this:

ps -ef | egrep sql

This would show you all the processes which include the string 'sql' somewhere in the line returned by ps. The egrep is searching across the whole line. If the username is 'mr_sql' then a line would be returned, and if the process is 'sqlplus' than a line would also be returned.

To do something similar in PowerShell you would do something more specific

get-process | where processname -like '*sql*'

So the string 'sql' has to match the contents of the property processname. As it happens, get-process by default only returns one text field, so in this case it's relatively academic, but hopefully it illustrates the point.

env

The Linux 'env' shows all the environment variables.

In PowerShell there are two set of environment variables:

• windows-level variables and

• Powershell-level variable

Windows-level variables are given by:

Get-ChildItem Env: | fl

PowerShell-level variables are given by:

get-variable

errpt

I think errpt is possibly just an AIX thing (the linux equivalent is, I think, looking at /var/log/message). It shows system error and log messages.

The PowerShell equivalent would be to look at the Windows eventlog, as follows

get-eventlog -computername bigserver -logname application -newest 15

The lognames that I typically look at are 'system', 'application' or 'security'.

export PS1="$ "

In bash the following changes the prompt when you are at the command line

export PS1="$ "

The Powershell equivalent to this is:

function prompt {
 "$ "
 }

I found this on Richard Siddaway's blog: http://msmvps.com/blogs/richardsiddaway/archive/2013/07/21/fun-with-prompts.aspx