Linked Questions
220 questions linked to/from What are the shell's control and redirection operators?
226
votes
3
answers
111k
views
What's the difference between semicolon and double ampersand && [duplicate]
What is the difference between
echo "Hello " ; echo "world"
and
echo "Hello " && echo "world"
Both seems to run the two commands after each other.
- 3,956
138
votes
4
answers
111k
views
What is the difference between "&&" and ";" when chaining commands [duplicate]
What is the difference between the following methods of chaining commands?
cmd1; cmd2
cmd1 && cmd2
- 2,286
46
votes
5
answers
39k
views
Is there a difference between `;` and `&&` and `|`? [duplicate]
When you want to run multiple commands you can use ;, && and |
Like this: killall Finder; killall SystemUIServer, cd ~/Desktop/ && rm Caches Or: man grep | man cat for example.
But, ...
- 11.2k
43
votes
3
answers
93k
views
What does ">" do vs ">>"? [duplicate]
I am currently doing preparation for my GCSE computing controlled assessment on Linux. I type ls > list and ls >> list into the command line, but it does not do anything. I have googled it ...
- 761
31
votes
3
answers
88k
views
What does || mean in bash? [duplicate]
Apologies if this is a duplicate post. I did try searching to see if someone already asked/answered this but didn't find anything.
What does || mean in bash? For example, in researching steps to ...
- 8,649
45
votes
2
answers
31k
views
Difference between executing multiple commands with && and ; [duplicate]
What's the difference between executing multiple commands with && and ;?
Examples:
echo "Hi\!" && echo "How are you?"
and
echo "Hi\!"; echo "How are you?"
- 553
32
votes
2
answers
70k
views
How do I run a command only after previous command is unsuccessful in bash? [duplicate]
We use && operator to run a command after previous one finishes.
update-system-configuration && restart-service
but how do I run a command only if previous command is unsuccessful ?
...
- 431
39
votes
2
answers
55k
views
What is &>> in a shell script [duplicate]
In a script I have inherited the output of one of our programs is put in to a file with:
program &>> result.txt
I have been reading in my book "Learning the bash shell" at home over the ...
- 391
38
votes
2
answers
35k
views
What does the < (left chevron / triangle bracket) do? [duplicate]
I understand that the > (right chevron) is for redirecting the STDOUT of a program to a file, as in echo 'polo' > marco.txt will create a text file called marco.txt with polo as the contents ...
- 576
33
votes
1
answer
14k
views
Difference between parentheses and braces in terminal? [duplicate]
( du /etc; du /var; ) > tmp.txt
{ du /etc; du /var; } > tmp.txt
Is there a difference between the () and {}?
The output of tmp.txt seems exactly the same, and I was wondering whether i'm ...
- 441
11
votes
2
answers
11k
views
How to redirect the output of a command to an already existing file without deleting its contents? [duplicate]
I am making a backup of some files and am creating a checksum file, checksums.txt, to later check the integrity of my data. However pasting each checksum manually into the file is inconvenient since ...
- 1,039
15
votes
1
answer
6k
views
POSIX compliant way to redirect stdout and stderr to a file [duplicate]
I am trying to write a script which is POSIX compliant, so it can run on any *nix system (Debian, Fedora, CentOS, AIX, Arch... ALL of them). When it comes to redirection, I am rather confused on what ...
- 417
8
votes
1
answer
17k
views
what is the difference between >&2 and &>2 [duplicate]
Just wondering if there is any difference between:
echo "running the npm patch" >&2;
and
echo "running the npm patch" &>2;
I have actually never really understand that syntax.
- 8,992
6
votes
2
answers
12k
views
What is the difference between > and >> (especially as it relates to use with the cat program)? [duplicate]
Suppose that I have a file called temp.txt. Using the cat program, I would like to add the contents of this file to the end of myfile.txt -- creating myfile.txt if it does not exist and appending to ...
- 15.8k
0
votes
1
answer
62k
views
How do I use: cat << EOF [duplicate]
I am little confused and not sure, how to add the cat << EOF style to my script. Would really appreciate a little feedback and help.
Here is my script
!/bin/sh
#This is a disk mailer script ...
