Questions tagged [bash]
**** IMPORTANT NOTE: Do not ask a bash question until after you have copy/pasted your script into http://shellcheck.net and fixed all of the issues it tells you about. **** This tag is for questions about scripts written for the Bash command shell. Questions about the interactive use of Bash are more likely to be on-topic on Unix & Linux Stack Exchange or Super User than on Stack Overflow.
156,277
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How do I get the directory where a Bash script is located from within the script itself?
How do I get the path of the directory in which a Bash script is located, inside that script?
I want to use a Bash script as a launcher for another application. I want to change the working directory ...
4470
votes
35
answers
3.3m
views
How do I check if a directory exists or not in a Bash shell script?
What command checks if a directory exists or not within a Bash shell script?
- 128k
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votes
21
answers
3.1m
views
How do I tell if a file does not exist in Bash?
This checks if a file exists:
#!/bin/bash
FILE=$1
if [ -f $FILE ]; then
echo "File $FILE exists."
else
echo "File $FILE does not exist."
fi
How do I only check if the ...
- 403k
3566
votes
30
answers
3.2m
views
How to check if a string contains a substring in Bash
I have a string in Bash:
string="My string"
How can I test if it contains another string?
if [ $string ?? 'foo' ]; then
echo "It's there!"
fi
Where ?? is my unknown operator. ...
- 39.5k
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votes
31
answers
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views
How to concatenate string variables in Bash
In PHP, strings are concatenated together as follows:
$foo = "Hello";
$foo .= " World";
Here, $foo becomes "Hello World".
How is this accomplished in Bash?
- 67.3k
3536
votes
24
answers
3.5m
views
Echo newline in Bash prints literal \n
How do I print a newline? This merely prints \n:
$ echo -e "Hello,\nWorld!"
Hello,\nWorld!
- 48.8k
3183
votes
19
answers
1.8m
views
What does " 2>&1 " mean?
To combine stderr and stdout into the stdout stream, we append this to a command:
2>&1
e.g. to see the first few errors from compiling g++ main.cpp:
g++ main.cpp 2>&1 | head
What does ...
- 68.6k
3148
votes
39
answers
1.2m
views
How can I check if a program exists from a Bash script?
How would I validate that a program exists, in a way that will either return an error and exit, or continue with the script?
It seems like it should be easy, but it's been stumping me.
- 36.9k
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votes
39
answers
3.6m
views
How do I split a string on a delimiter in Bash?
I have this string stored in a variable:
IN="[email protected];[email protected]"
Now I would like to split the strings by ; delimiter so that I have:
ADDR1="[email protected]"
ADDR2="[email protected]"
I don't ...
- 79k
2851
votes
40
answers
2.3m
views
Extract filename and extension in Bash
I want to get the filename (without extension) and the extension separately.
The best solution I found so far is:
NAME=`echo "$FILE" | cut -d'.' -f1`
EXTENSION=`echo "$FILE" | cut -d'.' -f2`
This ...
- 45.9k
2783
votes
33
answers
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views
How to change the output color of echo in Linux
I am trying to print a text in the terminal using echo command.
I want to print the text in a red color. How can I do that?
- 31.1k
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votes
44
answers
2.1m
views
How do I parse command line arguments in Bash?
Say, I have a script that gets called with this line:
./myscript -vfd ./foo/bar/someFile -o /fizz/someOtherFile
or this one:
./myscript -v -f -d -o /fizz/someOtherFile ./foo/bar/someFile
What's the ...
- 68.5k
2441
votes
38
answers
2.3m
views
How to check if a variable is set in Bash
How do I know if a variable is set in Bash?
For example, how do I check if the user gave the first parameter to a function?
function a {
# if $1 is set ?
}
- 188k
2436
votes
16
answers
2.9m
views
How do I set a variable to the output of a command in Bash?
I have a pretty simple script that is something like the following:
#!/bin/bash
VAR1="$1"
MOREF='sudo run command against $VAR1 | grep name | cut -c7-'
echo $MOREF
When I run this script from the ...
- 24.8k
2305
votes
21
answers
2.1m
views
Loop through an array of strings in Bash?
I want to write a script that loops through 15 strings (array possibly?) Is that possible?
Something like:
for databaseName in listOfNames
then
# Do something
end
- 41.7k