Hi all...

I have text1, text2, text3 in a directory

[vinay@localhost temp]$ echo text*
text1 text2 text3
[vinay@localhost temp]$ ls text*
text1 text2 text3
[vinay@localhost temp]$ echo "test*"
test*

Here I am not able to understand why the first echo command is taking ls commands feature ??

Please help me ...
Thanks in advance...

I would expect that is because of the special character *. the shell will interpret this as a regular expression, when you put it in quotes, it becomes a string.

still..why it should display filenames ? That is my question...i.e, it is taking ls command's feature

No it is not hijacking any features of ls.
You could understand that. Without any options to both the commands run those inside a directory and see what is the output.

Well this is an interesting find. I didn't even know echo could be used this way...

I believe the reason echo is behaving this way is because of the "*" after text. Echo first looks for any file with text in the beginning of its name, and prints it out as a string. I could be wrong, but that's my 0.02 cents.

Thanks for your reply...

I am running both ls and echo without options above as you have mentioned...But why echo * or echo text* is displaying file names ??

The regular expression seems to be matching anything in the current directory. It's got to match something...

DO NOT even use "*" as the option and then you will see. * matches everything in the directory and thats why it is giving the output. echo is used to output anything on screen and this what echo is doing.
Just type echo and press return and then see.

Thanks to everyone...Finally i understood the concept

Hi

Its actually an interview question mostly asked.
except ls command is there any other way to list the files of a directory in Linux?

1 ) ls
2 ) dir
3 ) echo *

Special meaning of metacharacter ( * ) is "not" being ignored when used out of double and single quotes.

Please note there no way to list hidden files using echo * command.
but this you can do by adding option -a with ls and dir command in Linux.

cheerzz!!

None of the explanations above seem very clear to me, and I am still not sure if some people understand.

The shell intercepts certain characters and performs operations on them BEFORE the command runs. In the case of "echo text*", bash changes "text*" to 'all files that start with text' before it calls echo. So in this case, the shell changes the command you've written to "echo text1 text2 text3". IOW, expanding patterns is not actually understood by ls, and you can see this by entering a directory with many many files and typing "ls *" - you can actually exceed the maximum command line length this way (I needed around 5000 files with quite long names). Escaping the * by surrounding it with double quotes or putting a backslash in front of it stops bash from doing this:

You can also see this with a small shell function:

Very Helpfull CroMagnon...Thanks a lot

It's called "Pathname Expansion" & you can find the formal explanation in the bash man page by searching for "After word splitting,".

In the GNU Bash Reference manual it is called filename expansion and you can find more than you ever wanted to know about it here.

In the strict sense, echo is not displaying file names. It is just displaying a string that it receives. Echo, unlike ls, has no concept of file names or whatever. The expansion happens before echo even gets into scene, to start with. All that echo receives is a string, and it effectively echoes that screen to stdout. The fact that that screen matches a list of file names is purely coincidental, and is due to the preliminary expansion that the shell does before passing the arguments to echo.