The permission bit in a file mode that allows a file to be run as a program. Also, questions related the format of program files, and to locating and executing program files.

learn more… | top users | synonyms

132
votes
4answers
30k views

How do I clear Bash's cache of paths to executables?

When I execute a program without specifying the full path to the executable, and Bash must search the directories in $PATH to find the binary, it seems that Bash remembers the path in some sort of ...
129
votes
9answers
18k views

How to chmod without /usr/bin/chmod?

Today I was told a tale by a Unix trainer, a tale where the root password got leaked to the students, and one of the fellas removed the execute permission from /usr/bin/chmod itself. How do you ...
124
votes
1answer
8k views

How is Mono magical?

I'm learning C#, so I made a little C# program that says Hello, World!, then compiled it with mono-csc and ran it with mono: $ mono-csc Hello.cs $ mono Hello.exe Hello, World! I noticed that when I ...
53
votes
1answer
5k views

Why does the following script delete itself?

If you create an executable file with the following contents, and run it, it will delete itself. How does this work? #!/bin/rm
42
votes
8answers
54k views

What is /usr/local/bin?

Before today, I've used the terminal to a limited extent of moving in and out of directories and changing the dates of files using the touch command. I had realised the full extent of the terminal ...
42
votes
2answers
27k views

Getting “Not found” message when running a 32-bit binary on a 64-bit system

I have currently a strange problem on debian (wheezy/amd64). I have created a chroot to install a server (i can't give any more detail about it, sorry). Let's call its path /chr_path/. To make things ...
36
votes
3answers
14k views

Does the shebang determine the shell which runs the script?

This may be a silly question, but I ask it still. If I have declared a shebang #!/bin/bash in the beginning of my_shell_script.sh, so do I always have to invoke this script using bash ...
35
votes
4answers
92k views

Why do we use “./” to execute a file?

Why do we use ./filename to execute a file in linux? Why not just enter it like other commands gcc, ls etc...
34
votes
6answers
19k views

Can a script be executable but not readable?

Is it possible to execute a script if there is no permission to read it? In root mode, I made a script and I want the other user to execute this script but not read it. I did chmod to forbid read and ...
34
votes
2answers
983 views

Why and how are some shared libraries runnable, as though they are executables?

On 32-bit Linux systems, invoking this $ /lib/libc.so.6 and on 64-bit systems this $ /lib/x86_64-linux-gnu/libc.so.6 in a shell, provides an output like this: GNU C Library stable release ...
32
votes
4answers
29k views

Where do executables look for shared objects at runtime

The title is pretty explicit. I understand how to define include shared objects at linking/compile time. However I still wonder how do executables look for the shared object (*.so libraries) at ...
30
votes
8answers
43k views

Different ways to execute a shell script

There a several ways to execute a script, the ones I know are: /path/to/script # using the path (absolute or relative) . script # using the . (dot) source script # using the `source` command ...
29
votes
4answers
1k views

Execution of possibly harmful program on Linux

I'm writing a program that will test programs written by students. I'm afraid that I can't trust them and I need to make sure that it won't end up badly for the computer running it. I was thinking ...
27
votes
4answers
14k views

What makes OSX programs not runnable on Linux?

I know there are many differences between OSX and Linux, but what makes them so totally different, that makes them fundamentally incompatible?
25
votes
6answers
22k views

Can we get compiler information from an elf binary?

Is there some chance to know how a binary was built, under Linux? (and or other Unix) Compiler, version, time, flags etc... I looked at readelf and couldn't find much, but there might be other ways ...
24
votes
1answer
19k views

What are stripped and not-stripped executables in Unix?

From man file, EXAMPLES $ file file.c file /dev/{wd0a,hda} file.c: C program text file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses ...
23
votes
1answer
988 views

How does Linux determine what facilities to use to run a (non-text) binary?

I understand that Linux uses shebang line to determine what interpreter to use for scripting languages, but how does it work for binaries? I mean I can run Linux binaries, and having installed both ...
23
votes
1answer
2k views

Why can't root execute when executable bits are not set?

root user can write to a file even if its write permissions are not set. root user can read a file even if its read permissions are not set. root user can cd into a directory even if its execute ...
22
votes
2answers
7k views

What is the difference between running “bash script.sh” and “./script.sh”?

If script.sh is just something typical like #!/bin/bash echo "Hello World!" Is there a preferred way to run the script? I think you first have to chmod it so it becomes executable?
21
votes
6answers
47k views

#!/bin/bash - no such file or directory

I've created a bash script but when I try to execute it, I get #!/bin/bash no such file or directory I need to run the command: bash script.sh for it to work. How can I fix this?
21
votes
4answers
2k views

Why updating a running Linux system is not problematic?

It's years I use Linux systems on a daily basis, and I never had major problems by updating a system when it was running, but I still wonder why this is possibile. Let me make an example. Suppose a ...
20
votes
1answer
9k views

Loading of shared libraries and RAM usage

I'm wondering about the way Linux manages shared libraries. (actually I'm talking about Maemo Fremantle, a Debian-based distro released in 2009 running on 256MB RAM). Let's assume we have two ...
20
votes
1answer
4k views

Shebang line with `#!/usr/bin/env command --argument` fails on Linux

I've got a simple script: #!/usr/bin/env ruby --verbose # script.rb puts "hi" On my OSX box, it runs fine: osx% ./script.rb hi However, on my linux box, it throws an error linux% ./script.rb ...
19
votes
4answers
10k views

Binary compatibility between Mac OS X and Linux

Brace yourselves, this question will likely appear naive and/or foolish, seeing as I am relatively new to the inner workings of unix like systems, and programming in general. Ready? Ok! I will go ...
19
votes
2answers
8k views

Where should a local executable be placed?

I have an executable for the perforce version control client (p4). I can't place it in /opt/local because I don't have root privileges. Is there a standard location where it needs to be placed under ...
19
votes
2answers
24k views

How to convert a shell script into a binary executable?

I want to convert my shell scripts into binary executable so that nobody else could edit or read it. Is there a way to convert it into a binary executable?
17
votes
1answer
3k views

What is Linux doing differently that allows me to remove/replace files where Windows would complain the file is currently in use?

The example I have is Minecraft. When running Bukkit on Linux I can remove or update the .jar files in the /plugins folder and simply run the 'reload' command. In Windows, I have to take the whole ...
17
votes
1answer
2k views

How to trick a particular command into thinking it is a different date?

How can I execute a command making it believe that is on a different date than system one? For instance, if I have this script: #!/usr/bin/env bash date +"%B %d, %Y" It prints the actual date: ...
16
votes
2answers
3k views

How are system commands like ls created?

I'm a *nux newbie and I have some doubts regarding *nix. I don't know which type of executable file is ls, whether it is .sh or .ksh or any other kind of system executable if it is, what is that? ...
15
votes
5answers
10k views

How can I use environment variables in my shebang?

I have a Python script that need to be run with a particular python installation. Is there a way to craft a shebang so that it runs with $FOO/bar/MyCustomPython?
15
votes
3answers
5k views

The way to use `/usr/bin/env sed -f ` in shebang?

Typing /usr/bin/env sed -f in terminal works. But if use it as a shebang, #!/usr/bin/env sed -f s/a/b/ The script will be fail to execute: /usr/bin/env: sed -f: No such file or directory I ...
15
votes
1answer
1k views

Why does the file command say that ELF binaries are for Linux 2.6.9?

Whenever I run file on an ELF binary I get this output: [jonescb@localhost ~]$ file a.out a.out: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.6.9, dynamically linked ...
15
votes
2answers
37k views

sudo: unable to execute ./script.sh: no such file or directory

I'm stumped. I have a script in my /home directory which is executable: [user@server ~]$ ll total 4 -rwx------ 1 user user 2608 Jul 15 18:23 qa.sh However, when I attempt to run it with sudo it ...
14
votes
3answers
43k views

Viewing Linux Library / Executable version info

In Windows, EXE and DLL have version info, including at least the following fields: file version product version internal name product name copyright In Linux Library / Executable: Which fields ...
11
votes
2answers
1k views

Run a binary owned by root without sudo

I had a question on a job interview: How can you execute (run) the program with the user user1 without sudo privileges and without access to the root account: $ whoami user1 $ ls -l ...
11
votes
2answers
4k views

Test whether Linux binary is compiled as position independent code

I recently learned that (at least on Fedora and Red Hat Enterprise Linux), executable programs that are compiled as Position Independent Executables (PIE) receive stronger address space randomization ...
11
votes
1answer
1k views

When can I edit strings in an executable binary?

I have an executable binary; let's call it a.out. I can see the binary contains strings $ strings a.out ... /usr/share/foo .... I need to change the string /usr/share/foo to /usr/share/bar. Can I ...
11
votes
2answers
13k views

Why does sshd requires an absolute path?

Why does sshd require an absolute path when restarting, e.g /usr/sbin/sshd rather than sshd Are there any security implications? P.S the error message: # sshd sshd re-exec requires execution with ...
11
votes
3answers
6k views

Creating Static Binary

I installed an application [ e.g. fdisk ]. But it required libraries for execution. I am looking for utility/tool which will help me to create a static binary from already installed binaries. So that ...
10
votes
2answers
373 views

Why do so many programs live in PATH?

One thing that puzzles me about desktop Linux, at least, is that just about everything is in my PATH. By everything, I mean every desktop application, including things like gnome-character-map and ...
10
votes
3answers
1k views

Is there a way to execute a native binary from a pipe?

echo 'main(){}' | gcc -xc - -o /dev/stdout | ??? Is there a way to run the output binary on a unix-like system? EDIT: I needed it to run the output of g++ in a sandboxed environment where I can't ...
10
votes
2answers
747 views

How does a shell execute a program?

If I compile a program using gcc, and try to execute it from the bash shell, what is the exact sequence of steps followed by bash to execute it ? I know fork(), execve(), loader, dynamic linker (and ...
9
votes
4answers
603 views

How to install executables

I sometimes run into software that is not offered in .deb or .rpm but only as an executable. For example Visual Studio Code, WebStorm or Kerbal Space Programm. For this question, I will take Visual ...
9
votes
1answer
3k views

How to run my own program without specifying its path

Let's suppose I have compiled something and I run it like so: $ /path/to/my/executable/mycmd Hello World What do I need to do to run it like $ mycmd Hello World from everywhere in my computer? ...
9
votes
2answers
55k views

./executable: cannot execute binary file

I have a script that works well when I ssh to the server to execute it myself, but has problems when Hudson, a continuous integration server, runs it. I am automating tests on an embedded linux ...
8
votes
1answer
17k views

No such file or directory but I can see it!

I'm trying to run a python script, on a headless Raspberry PI using winSCP and get the following error message: Command '"./areadetect_movie_21.py"' failed with return code 127 and error message ...
8
votes
7answers
2k views

List all binaries from $PATH

Is there one-liner that will list all executables from $PATH in bash.
8
votes
2answers
1k views

vim: create file with +x bit

Is there any way to set +x bit on script while creating? For example I run: vim -some_option_to_make_file_executable script.sh and after saving I can run file without any additional movings. ps. ...
8
votes
3answers
643 views

where to put binaries so they are always in path and can be found easily

I am making quite some binaries, scripts etc that I want to install easily (using my own rpms). Since I want them accessible for everyone, my intuition would be to put them in /usr/bin; no need to ...
8
votes
2answers
775 views

Detect if an ELF binary was built with gprof instrumentation?

Is it possible to check if given program was compiled with GNU gprof instrumentation, i.e. with '-pg' flag passed to both compiler and linker, without running it to check if it would generate a ...