With that logic this echoes "echo". Question about echo!


 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting With that logic this echoes "echo". Question about echo!
# 1  
Old 11-11-2010
Hammer & Screwdriver With that logic this echoes "echo". Question about echo!

Code:
echo `echo `

doesn't echoes anything. And it's logic. But
Code:
echo `echo `echo ` `

does echoes "echo". What's the logic of it? the `echo `echo ` inside of the whole (first) echo, echoes nothing, so the first echo have to echo nothing but echoes "echo"

(too much echoing :P)Smilie
# 2  
Old 11-11-2010
That is because backticks have to be escaped if you nest them:
Code:
echo `echo \`echo \` `

You do not need to with the more modern $(..) command substitution construct:
Code:
 echo $(echo $(echo))

# 3  
Old 11-11-2010
Thx, it seems interesting Smilie
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. UNIX for Beginners Questions & Answers

Basic question on "echo"

what happens when I echo asterisk? Please don't hijack other peoples' thread; post our own new one as required by forum rules! (5 Replies)
Discussion started by: ithenr00
5 Replies

2. UNIX for Dummies Questions & Answers

Difference between echo `ls -l` and echo "`ls -l`" ?

Hi guys, Been messing around with shell programming for a couple of days and I found something that was pretty odd in the behavior of the echo command. Below is an example-: When I type the following in my /home directory from my lxterminal in Debian-: echo "`ls -l`" I get the... (2 Replies)
Discussion started by: sreyan32
2 Replies

3. Shell Programming and Scripting

tcsh - understanding difference between "echo string" and "echo string > /dev/stdout"

I came across and unexpected behavior with redirections in tcsh. I know, csh is not best for redirections, but I'd like to understand what is happening here. I have following script (called out_to_streams.csh): #!/bin/tcsh -f echo Redirected to STDOUT > /dev/stdout echo Redirected to... (2 Replies)
Discussion started by: marcink
2 Replies

4. AIX

echo $varibla | mail -s "subject" "xxx@xxx.com" not ruuning as expected

Hi Folks, As per the subject, the following command is not working as expected. echo $variable | mail -s "subject" "xxx@xxx.com" Could anyone figure it out whats wrong with this. I am using AIX box. Regards, (2 Replies)
Discussion started by: gjarms
2 Replies

5. Shell Programming and Scripting

cmd || echo "something" - doesn't exit uppon error

Hi guys, I have a shell script where I have the following: for i in ad0 ad1 do gpart create -s gpt $i || echo "Cannot create GPT partition on "$i". Exiting ..." gpart add -s 128 -t freebsd-boot $i || echo "Cannot add freebsd-boot partition on "$i". Exiting ..." gpart add -s 4G -t... (2 Replies)
Discussion started by: da1
2 Replies

6. Shell Programming and Scripting

"Simple" echo/reading variable question...

Hello, I have a simple(I think) question! Although simple, I have been unable to resolve it, so I hope someone can help! OK, here it is: 1)I have an awk script that prints something, such as: awk '{print $2}' a > x so x might hold the value of say '10' 2)Now, I just want to check to see if... (4 Replies)
Discussion started by: astropi
4 Replies

7. Shell Programming and Scripting

ksh script that echo " please insert your name " and store the output to a login.log file.

Hello All Nice to meet you all here in this forum, it's my 1rst time here i'm asking about a little issue that i face i added a ksh script that echo " please insert your name " and store the output to a login.log file. the script is working fine with normal telnet but Xstart is not working... (8 Replies)
Discussion started by: islam.said
8 Replies

8. Shell Programming and Scripting

Difference between using "echo" builtin and /bin/echo

So in my shell i execute: { while true; do echo string; sleep 1; done } | read line This waits one second and returns. But { while true; do /bin/echo string; sleep 1; done } | read line continues to run, and doesn't stop until i kill it explicitly. I have tried this in bash as well as zsh,... (2 Replies)
Discussion started by: ulidtko
2 Replies

9. Shell Programming and Scripting

"sed" to check file size & echo " " to destination file

Hi, I've modified the syslogd source to include a thread that will keep track of a timer(or a timer thread). My intention is to check the file size of /var/log/messages in every one minute & if the size is more than 128KB, do a echo " " > /var/log/messages, so that the file size will be set... (7 Replies)
Discussion started by: jockey007
7 Replies

10. Solaris

question for "echo"

what is the mean: echo -n "^0;!*^G" thanks (3 Replies)
Discussion started by: chris_chang
3 Replies
Login or Register to Ask a Question

Featured Tech Videos