Questions tagged [linux]
NOTICE: All Linux questions must be related to programming; those that aren't will be closed. Use this tag only if your question relates to programming using Linux APIs or Linux-specific behavior, not just because you happen to run your code on Linux. If you need Linux support, you can try https://unix.stackexchange.com or the specific Linux distribution's Stack Exchange site like https://askubuntu.com or https://elementaryos.stackexchange.com/
linux
227,860
questions
7535
votes
56
answers
11.2m
views
Find all files containing a specific text (string) on Linux?
How do I find all files containing a specific string of text within their file contents?
The following doesn't work. It seems to display every single file in the system.
find / -type f -exec grep -H '...
- 76.8k
3029
votes
19
answers
4.6m
views
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?
- 34.8k
2780
votes
33
answers
2.0m
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
2424
votes
7
answers
1.7m
views
How do I delete an exported environment variable?
Before installing gnuplot, I set the environment variable GNUPLOT_DRIVER_DIR = /home/gnuplot/build/src. During the installation, something went wrong.
I want to remove the GNUPLOT_DRIVER_DIR ...
- 36.8k
2233
votes
18
answers
2.3m
views
How can I symlink a file in Linux? [closed]
I want to create a symbolic link in Linux. I have written this Bash command where the first path is the folder I want to link, and the second path is the compiled source.
ln -s '+basebuild+'/IpDome-...
- 41.2k
2216
votes
49
answers
1.8m
views
How do I exclude a directory when using `find`?
How do I exclude a specific directory when searching for *.js files using find?
find . -name '*.js'
- 36.6k
2191
votes
27
answers
2.3m
views
How do I recursively grep all directories and subdirectories?
How do I recursively grep all directories and subdirectories?
find . | xargs grep "texthere" *
- 22.1k
2177
votes
19
answers
5.2m
views
How do I change permissions for a folder and its subfolders/files? [closed]
How do I change the permissions of a folder and all its subfolders and files?
This only applies to the /opt/lampp/htdocs folder, not its contents:
chmod 775 /opt/lampp/htdocs
How do I set chmod 755 ...
- 58.1k
2153
votes
20
answers
723k
views
How do I profile C++ code running on Linux?
How do I find areas of my code that run slowly in a C++ application running on Linux?
- 26.1k
2125
votes
16
answers
2.8m
views
Looping through the content of a file in Bash
How do I iterate through each line of a text file with Bash?
With this script:
echo "Start!"
for p in (peptides.txt)
do
echo "${p}"
done
I get this output on the screen:
Start!
./runPep.sh: ...
- 31.3k
1887
votes
39
answers
1.4m
views
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?
- 43.1k
1809
votes
5
answers
203k
views
What is ':-!!' in C?
I bumped into this strange macro code in /usr/include/linux/kernel.h:
/* Force a compilation error if condition is true, but also produce a
result (of value 0 and type size_t), so the expression ...
- 15.1k
1614
votes
12
answers
1.1m
views
How to redirect output to a file and stdout
In bash, calling foo would display any output from that command on the stdout.
Calling foo > output would redirect any output from that command to the file specified (in this case 'output').
Is ...
- 58.6k
1568
votes
23
answers
1.2m
views
Merge / convert multiple PDF files into one PDF [closed]
How could I merge / convert multiple PDF files into one large PDF file?
I tried the following, but the content of the target file was not as expected:
convert file1.pdf file2.pdf merged.pdf
I need ...
- 23.5k
1494
votes
3
answers
1.1m
views
How can I use grep to show just filenames on Linux? [closed]
How can I use grep to show just file-names (no in-line matches) on Linux?
I am usually using something like:
find . -iname "*php" -exec grep -H myString {} \;
How can I just get the file-...
- 54.2k
1481
votes
35
answers
2.9m
views
How to kill a process running on particular port in Linux?
I tried to close the tomcat using ./shutdown.sh from tomcat /bin directory. But found that the server was not closed properly. And thus I was unable to restartMy tomcat is running on port 8080.
I ...
- 21.1k
1464
votes
3
answers
2.9m
views
How do I create a copy of a directory in Unix/Linux? [closed]
I want to recursively create a copy of a directory and all its contents (e.g. files and subdirectories).
- 14.7k
1411
votes
28
answers
1.8m
views
How to count lines in a document? [closed]
I have lines like these, and I want to know how many lines I actually have...
09:16:39 AM all 2.00 0.00 4.00 0.00 0.00 0.00 0.00 0.00 94.00
09:16:40 AM all 5.00 0.00 ...
- 16.9k
1362
votes
28
answers
3.7m
views
How can I close some specific port on Linux? [closed]
How can I remove the port that some application/process has used it but didn't close the port?
For example: when I run ssh on my ubuntu and tunnel the ssh connection on some port <PORT> on my ...
- 41.9k
1360
votes
24
answers
1.1m
views
Which version of PostgreSQL am I running?
I'm in a corporate environment (running Debian Linux) and didn't install it myself. I access the databases using Navicat or phpPgAdmin (if that helps). I also don't have shell access to the server ...
- 39.4k
1305
votes
31
answers
824k
views
Pipe to/from the clipboard in a Bash script
Is it possible to pipe to/from the clipboard in Bash?
Whether it is piping to/from a device handle or using an auxiliary application, I can't find anything.
For example, if /dev/clip was a device ...
- 137k
1239
votes
15
answers
510k
views
Defining a variable with or without export
What is export for?
What is the difference between:
export name=value
and
name=value
- 269k
1206
votes
29
answers
1.3m
views
Using ls to list directories and their total sizes [closed]
Is it possible to use ls in Unix to list the total size of a sub-directory and all its contents as opposed to the usual 4K that (I assume) is just the directory file itself?
total 12K
drwxrwxr-x 6 **...
- 17k
1196
votes
10
answers
1.0m
views
Remove a symlink to a directory [closed]
I have a symlink to an important directory. I want to get rid of that symlink, while keeping the directory behind it.
I tried rm and get back rm: cannot remove 'foo'.
I tried rmdir and got back rmdir: ...
- 15.4k
1139
votes
14
answers
764k
views
How can I exclude directories from grep -R?
I want to traverse all subdirectories, except the node_modules directory.
- 268k
1139
votes
12
answers
717k
views
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
set -e
# ...
- 42.3k
1131
votes
15
answers
346k
views
How do I use sudo to redirect output to a location I don't have permission to write to? [closed]
I've been given sudo access on one of our development RedHat linux boxes, and I seem to find myself quite often needing to redirect output to a location I don't normally have write access to.
The ...
- 26.4k
1120
votes
31
answers
1.3m
views
Shell command to tar directory excluding certain files/folders [closed]
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 ...
- 20.7k
1109
votes
5
answers
135k
views
Why does the C preprocessor interpret the word "linux" as the constant "1"?
Why does the C preprocessor in GCC interpret the word linux (small letters) as the constant 1?
test.c:
#include <stdio.h>
int main(void)
{
int linux = 5;
return 0;
}
Result of $...
- 7,825
1108
votes
26
answers
945k
views
Recursively counting files in a Linux directory
How can I recursively count files in a Linux directory?
I found this:
find DIR_NAME -type f ¦ wc -l
But when I run this it returns the following error.
find: paths must precede expression: ¦
- 11.7k
1101
votes
33
answers
1.3m
views
Exploring Docker container's file system
I've noticed with docker that I need to understand what's happening inside a container or what files exist in there. One example is downloading images from the docker index - you don't have a clue ...
- 41.3k
1094
votes
24
answers
2.1m
views
How to permanently set $PATH on Linux/Unix [closed]
On Linux, how can I add a directory to the $PATH so it remains persistent across different sessions?
Background
I'm trying to add a directory to my path so it will always be in my Linux path. I've ...
- 266k
1093
votes
14
answers
1.3m
views
Where can I find php.ini?
Today I needed to install the IBM DB2 library. I went through all the steps up to make install, and I found ibm_db2.so in $PHP_HOME/lib/extensions/somecomplicatedname/ibm_db2.so.
The great catch is ...
- 24.4k
1056
votes
36
answers
1.7m
views
How to get full path of a file?
Is there an easy way I can print the full path of file.txt ?
file.txt = /nfs/an/disks/jj/home/dir/file.txt
The <command>
dir> <command> file.txt
should print
/nfs/an/disks/jj/...
- 22.3k
1035
votes
13
answers
1.7m
views
How does "cat << EOF" work in bash?
I needed to write a script to enter multi-line input to a program (psql).
After a bit of googling, I found the following syntax works:
cat << EOF | psql ---params
BEGIN;
`pg_dump ----...
- 165k
1021
votes
2
answers
1.7m
views
How can I get the current date and time in the terminal and set a custom command in the terminal for it? [closed]
I have to check the time in a Linux terminal.
What is the command for getting date and time in a Linux terminal?
Is there a way in which we can set a custom function?
- 10.6k
1002
votes
10
answers
691k
views
Given two directory trees, how can I find out which files differ by content? [closed]
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 in ...
- 21.4k
956
votes
19
answers
1.4m
views
open() in Python does not create a file if it doesn't exist
What is the best way to open a file as read/write if it exists, or if it does not, then create it and open it as read/write? From what I read, file = open('myfile.dat', 'rw') should do this, right?
It ...
- 11.5k
924
votes
9
answers
1.4m
views
Redirect all output to file in Bash [duplicate]
I know that in Linux, to redirect output from the screen to a file, I can either use the > or tee. However, I'm not sure why part of the output is still output to the screen and not written to the ...
- 14.6k
911
votes
32
answers
1.5m
views
How can I measure the actual memory usage of an application or process?
How do you measure the memory usage of an application or process in Linux?
From the blog article of Understanding memory usage on Linux, ps is not an accurate tool to use for this intent.
Why ps is &...
- 16.8k
905
votes
7
answers
846k
views
Get current time in seconds since the Epoch on Linux, Bash
I need something simple like date, but in seconds since 1970 instead of the current date, hours, minutes, and seconds.
date doesn't seem to offer that option. Is there an easy way?
- 15.1k
895
votes
19
answers
1.6m
views
How to force cp to overwrite without confirmation
I'm trying to use the cp command and force an overwrite.
I have tried cp -rf /foo/* /bar, but I am still prompted to confirm each overwrite.
- 10.6k
883
votes
31
answers
923k
views
Argument list too long error for rm, cp, mv commands
I have several hundred PDFs under a directory in UNIX. The names of the PDFs are really long (approx. 60 chars).
When I try to delete all PDFs together using the following command:
rm -f *.pdf
I ...
- 17.2k
881
votes
13
answers
441k
views
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 me.
I've tried ...
- 49k
871
votes
2
answers
381k
views
How do SO_REUSEADDR and SO_REUSEPORT differ?
The man pages and programmer documentations for the socket options SO_REUSEADDR and SO_REUSEPORT are different for different operating systems and often highly confusing. Some operating systems don't ...
- 131k
868
votes
70
answers
2.7m
views
Cannot connect to the Docker daemon at unix:/var/run/docker.sock. Is the docker daemon running?
I have applied every solution available on internet but still I cannot run Docker.
I want to use Scrapy Splash on my server.
Here is history of commands I ran.
docker run -p 8050:8050 scrapinghub/...
- 20.6k
866
votes
19
answers
1.9m
views
Sleep for milliseconds
I know the POSIX sleep(x) function makes the program sleep for x seconds. Is there a function to make the program sleep for x milliseconds in C++?
- 13.1k
866
votes
25
answers
733k
views
How can I copy the output of a command directly into my clipboard?
How can I pipe the output of a command into my clipboard and paste it back when using a terminal? For instance:
cat file | clipboard
- 116k
863
votes
14
answers
736k
views
How to kill all processes with a given partial name? [closed]
I want to kill all processes that I get by:
ps aux | grep my_pattern
How to do it?
This does not work:
pkill my_pattern
- 49.7k
863
votes
11
answers
2.1m
views
Kill detached screen session [closed]
I learned from somewhere a detached screen can be killed by
screen -X -S [session # you want to kill] kill
where [session # you want to kill] can be gotten from
screen -ls
But this doesn't work. ...
- 97.8k