32 Answered Questions for the topic shell
./configure : /bin/sh^M : bad interpreter?
I've been trying to install lpng142 on my fed 12 system. Seems like a problem to me. I get this error
[root@localhost lpng142]# ./configure
bash: ./configure: /bin/sh^M: bad interpreter: No such...
more
How do I test if a variable is a number in Bash?
I just can't figure out how do I make sure an argument passed to my script is a number or not.
All I want to do is something like this:
test *isnumber* $1 && VAR=$1 || echo "need a...
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Defining a variable with or without export?
What is `export` for?
What is the difference between:
export name=value
and
name=value
Shell Linux
06/20/19
How can I recursively find all files in current and subfolders based on wildcard matching?
How can I recursively find all files in current and subfolders based on wildcard matching?
Shell Linux
06/20/19
Why doesn't "cd" work in a shell script?
I'm trying to write a small script to change the current directory to my project directory:
#!/bin/bash
cd /home/tree/projects/java
I saved this file as proj, added execute permission with...
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How to append one file to another in Ubuntu Linux?
I have two files: `file1` and `file2`. How do I append the contents of `file2` to `file1` so that contents of `file1` persist the process?
What's the best way to send a signal to all members of a process group?
I want to kill a whole process tree. What is the best way to do this using any common scripting languages? I am looking for a simple solution.
What does set -e mean in a bash script?
I'm studying the content of this **preinst** file that the script executes before that package is unpacked from its Debian archive (.deb) file.
The script has the following code:
#!/bin/bash
...
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Get program execution time in the shell?
I want to execute something in a linux shell under a few different conditions, and be able to output the execution time of each execution.
I know I could write a perl or python script that would...
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06/08/19
Calling an external command in Python?
How can I call an external command (as if I'd typed it at the Unix shell or Windows command prompt) from within a Python script?
Shell command to tar directory excluding certain files/folders?
Is there a simple shell command/script that supports excluding certain files/folders from being archived?
I have a directory that need to be archived with a sub directory that has a number of very...
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Delete newline in Vim?
Is there a way to delete the newline at the end of a line in Vim, so that the next line is appended to the current line?
For example:
Evaluator<T>():
_bestPos(){
}
I'd like to put this...
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Given two directory trees, how can I find out which files differ?
If I want find the differences between two directory trees, I usually just execute:
diff -r dir1/ dir2/
This outputs exactly what the differences are between corresponding files. I'm interested...
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How to exclude a directory in find . command?
I'm trying to run a `find` command for all JavaScript files, but how do I exclude a specific directory?
Here is the `find` code we're using.
for file in $(find . -name '*.js')
do
java -jar...
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How to represent multiple conditions in a shell if statement?
I want to represent multiple conditions like this:
if [ ( $g -eq 1 -a "$c" = "123" ) -o ( $g -eq 2 -a "$c" = "456" ) ]
then
echo abc;
else
echo efg;
fi
but when I execute the script,...
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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
05/26/19
How to assign name for a screen?
I'm using the `screen` multiplexer tool on the command shell and open a lot of screens. I then forget which process ID associates with which task.
I would like to set a name for a screen but can't...
more
05/20/19
How to determine whether a given Linux is 32 bit or 64 bit?
When I type `uname -a`, it gives the following output.
Linux mars 2.6.9-67.0.15.ELsmp #1 SMP Tue Apr 22 13:50:33 EDT 2008 i686 i686 i386 GNU/Linux
How can I know from this that the given OS is...
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How to read a file into a variable in shell?
I want to read a file and save it in variable, but I need to keep the variable and not just print out the file.
How can I do this? I have written this script but it isn't quite what I needed:
...
more
05/18/19
How can I reverse the order of lines in a file?
I'd like to reverse the order of lines in a text file (or stdin), preserving the contents of each line.
So, i.e., starting with:
foo
bar
baz
I'd like to end up with
baz
bar
foo
Is there...
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How do I prompt for Yes/No/Cancel input in a Linux shell script?
I want to pause input in a shell script, and prompt the user for choices. The standard 'Yes, No, or Cancel' type question. How do I accomplish this in a typical bash prompt?
How do I know the script file name in a Bash script?
How can I determine the name of the Bash script file inside the script itself?
Like if my script is in file `runme.sh`, then how would I make it to display "You are running runme.sh" message...
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Aborting a shell script if any command returns a non-zero value?
I have a Bash shell script that invokes a number of commands.
I would like to have the shell script automatically exit with a return value of 1 if any of the commands return a non-zero value.
Is...
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Bash tool to get nth line from a file?
Is there a "canonical" way of doing that? I've been using `head -n | tail -1` which does the trick, but I've been wondering if there's a Bash tool that specifically extracts a line (or a range of...
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How to 'grep' a continuous stream?
Is that possible to use `grep` on a continuous stream?
What I mean is sort of a `tail -f <file>` command, but with `grep` on the output in order to keep only the lines that interest...
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