what's the difference of these two commands?


 
Thread Tools Search this Thread
Top Forums UNIX for Dummies Questions & Answers what's the difference of these two commands?
# 1  
Old 04-25-2005
what's the difference of these two commands?

shouldn't they give the same output?

echo `echo \`date\``
is the same as the command date

echo `echo date`
prints the word date


thanks!
# 2  
Old 04-25-2005
echo `echo \`date\`` - due to the back ticks, the shell will complete the `date` portion, then echo it back to you (a waste of processor since date automatically puts it to standard out.


echo `echo date` - yes, it does print the word date since that is what you told it to do - echo date - not echo the output of the command date. You could set up a variable such as today to show it.
today="date"
echo $today
today=`date`
echo $today
# 3  
Old 04-25-2005
Code:
echo `echo \`date\``
is the same as the command date

Evaluation starts from the innermost command. Here, 'date' is inside back quotes '`', which means that the command has to be executed. The '\' is to escape the meaning of the '`' from the shell. The output of the date command goes to echo, which obviously echoes the same. This output in turn goes to the outermost echo command which again echoes the input to the output.

Code:
echo `echo date`
prints the word date

Here, the inner echo has as its input the word date - not the command. It echoes 'date', which is input to the outermost echo, which again echoes 'date'.

Cheers
# 4  
Old 04-25-2005
thanks guys !!
 
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Solaris

Difference between commands

i need to know the difference between two commands ps -ef|grep oracle ps -ef|grep -v grep |grep oracle (1 Reply)
Discussion started by: smazshah
1 Replies

2. Shell Programming and Scripting

Difference between these cron commands

Hi all I want to make sure I was understanding this correctly if a cron job command was * */20 * * * command does that mean this command will run every 20 hours? also what is the difference between the following two? 0,20,40 * * * * command 20 * * * * command I believe the first... (3 Replies)
Discussion started by: subway69
3 Replies

3. AIX

HACMP: difference between 'cl' commands and 'cli' commands

Hi all, I'm new in this forum. I'm looking for the difference between the HACMP commands with the prefix "cl" and "cli". The first type are under /usr/es/sbin/cluster/sbin directory and the second are under /usr/es/sbin/cluster/cspoc directory. I know that the first are called HACMP for AIX... (0 Replies)
Discussion started by: peppix
0 Replies

4. Solaris

Performance difference between commands

Looking at the performance hit on my server, does it matter wich command I run? client # rsh server tar –cf - . | tar –cv –f – or server # tar –cf – . | rsh client ‘cd target && tar –xv -f –‘ I think it doesn't really matter because both command strings involve a tar being run on... (4 Replies)
Discussion started by: petervg
4 Replies

5. Shell Programming and Scripting

Difference between 2 grep - commands

Hi, I need to know the difference between this commands: grep * *search* grep "*" *search* As far as i know does the 2nd command search for files which have a name with *search* and greps then all which have chars from a-z in the file content. But was does the first command?? Best... (1 Reply)
Discussion started by: xus
1 Replies

6. UNIX for Dummies Questions & Answers

Check for difference in output of 2 commands?

Hello! I'm just learning the shell, and I would really like to know how to do this: Given these 2 commands: ls -l ls -le How can I, with a one-liner, ask the shell to show me visually in the shell, what the difference is between the output of the two commands? They look the same to me... (6 Replies)
Discussion started by: turbofayce
6 Replies

7. Shell Programming and Scripting

Difference between the commands

HI all, Please clarify the difference between the following pm2srv:/var/opt/temip/vf/scripts/saiki#awk '{RS = ":"} ; {print $0}' testf2 hey:wasup:howru: Yes I am fine pm2srv:/var/opt/temip/vf/scripts/saiki#awk 'BEGIN { RS = ":" } ; { print $0 }' testf2 hey wasup howru Yes I... (0 Replies)
Discussion started by: saiki
0 Replies

8. Shell Programming and Scripting

Difference in auth key commands?

Good morning! What is the difference between: ssh-keygen -t rsa and ssh-keygen -b 2048 -t rsa? Thanks Bigben (2 Replies)
Discussion started by: bigben1220
2 Replies

9. UNIX for Dummies Questions & Answers

Difference in commands

Hello All, I have a question about the difference between two commands. I am using Korn and was told by the Unix admin that 'nohup <command> &' equals 'nohup ./<command> &. That there is no difference betwewen the two. Is this true? Also, does the command './<command> &' provide a disconnect... (4 Replies)
Discussion started by: grin1dan
4 Replies

10. Solaris

difference between these commands??

Hi, I would like to know what is the difference between executing the mount command in the following ways... eg: /usr/sbin/mount -F <something> AND mount -F <something> I mean , just executing the mount command as opposed to specifying the path and then executing it? ... (3 Replies)
Discussion started by: wrapster
3 Replies
Login or Register to Ask a Question