The shell is unix's command-line interface. You can type commands in a shell interactively, or write scripts to automate tasks. Use this tag for questions applying to /bin/sh and most compatible shells (ash, bash, ksh, zsh, …).

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2
votes
2answers
496 views

How to open process substituted file from php?

Here's what I tried to do myself: $ type 1.sh #!/bin/bash -eu php -r 'var_dump(file_get_contents($_SERVER["argv"][1]));' -- <(echo 1) $ ./1.sh PHP Warning: file_get_contents(/dev/fd/63): failed ...
3
votes
1answer
4k views

Easiest way to mount Google Cloud Storage in CentOS

we use centos for some hosting projects, but nut very expertise with systems. We pretend to use a main CentOS box to mount an "unlimited" Google Cloud Drive and then share it via NFS to the rest of ...
3
votes
1answer
55 views

Customize bash to always include a certain parameter

When using the "ls" command, bash prints in the following format: file1 file2 file3 file4 file5 file6 file7 file8 But when given the parameter "-1", it prints: file1 file2 file3 etc... Is there ...
5
votes
3answers
808 views

What is the difference having double quotes or not in bash [duplicate]

I have some bash scripts, one which has the following content: #!/bin/bash source $(dirname ${BASH_SOURCE[0]})/script.sh while the other one has the following content: #!/bin/bash source ...
2
votes
2answers
1k views

How do I run a command on a TTY from a SSH session?

Does anyone know of a way that I could run a command from my ssh session and have it display on tty1? It seems like I could do that like: script command >> /dev/tty1. However, if I were to do ...
0
votes
0answers
40 views

Convert rgba color value to a Terminal supported color

Randomly I will take the following example: rgba(122, 143, 186, 0.54) How can I convert this color to the closest Terminal supported color?
3
votes
6answers
760 views

When does a shell get executed during the linux startup process

I do not understand when does a shell, lets say bash, get executed, which program runs bash initially first.
2
votes
2answers
583 views

About escape with SSH pipe

I want to execute the awk command with long parameters,like this: ssh host "netstat -rn|awk 'NR!=1 && NF>=6 && $1!="Destination" {printf "%-15s %-20s\n", $1, $2}'|sort -f " but ...
12
votes
6answers
807 views

How can I cleanly add to $PATH?

I'd like a way to add things to $PATH, system-wide or for an individual user, without potentially adding the same path multiple times. One reason to want to do this is so that additions can be made ...
3
votes
1answer
96 views

What is 'ls quote'?

Today I happened to press ' after ls So the command is ls' After I issued this command: [edit]Seems the image can't display properly > ls' quote> ls' zsh: command not found: ls\nls > ...
1
vote
3answers
3k views

How to display “human-readable” file sizes in find results?

I'm trying to find all large files on my Centos server. To do that I'm using: find / -maxdepth 10 -size +100000 -ls I tried changing -ls to -lsh but it is not allowed. How can I display these ...
3
votes
1answer
3k views

Linux : how to redirect stdout & stderr to logger?

I have a program I need to run at startup, it has output on stdout and stderr that I want to redirect to the system log using the logger command. What I have in my startup script is thie: ...
9
votes
4answers
478 views

Terminate every background process

I have a few Stopped background processes. kill $(jobs -p) and kill `jobs -p` have no effect kill %1, kill %2, etc. successfully terminate individual processes How can I kill every background ...
1
vote
0answers
15 views

sticky alias command [duplicate]

I want to have the alias inst to be used instead of installpkg /tmp/ and then install packages by inst <pkg name>. But in normal alias define, We can not stick alias name to the package name and ...
1
vote
1answer
80 views

How do I display a manpage with groff in/on msysgit?

I've been unable to correctly set up a MANPATH environment variable in msysgit (1.9.0; 20140217) on Windows 7 (which is not my main concern here). Every time I execute the man command, I recieve the ...
15
votes
3answers
2k views

Why isn't there any shell command to create files?

Attention please: I am not asking how to make a file from the command line! I have been using touch for making files for years without paying attention that its main purpose is something else. If ...
1
vote
1answer
116 views

How to check for a folder inside a particular folder in shell script?

I am working on a shell script and python script as well. Python script is passing certain parameters to my shell script and then I am using those parameters in my shell script. Below is my shell ...
2
votes
1answer
79 views

Conditionals for fish shell

I am going through the fish shell tutorial and find that this simple if-else block does not work if grep fish /etc/shells echo Found fish else if grep bash /etc/shells echo ...
5
votes
2answers
336 views

Get the actions for a command programmatically

Let's take the git example: $ git<TAB><TAB> git git-import-dscs git-shell git-buildpackage git-import-orig git-upload-archive git-dch git-pbuilder ...
4
votes
2answers
6k views

Shell script wait for background command

I am writing a script, but there is something I need that I can't find a way to do it... I need to make a command in background "command1 &" and then somewhere in the script I need to wait for it ...
1
vote
2answers
130 views

tar specific files based on a pattern

I got a lot of files with the following format: 2014_04_01_11.txt 2014_04_01_12.txt 2014_04_01_13.txt 2013_03_25_12.txt 2013_04_29_15.txt I would like to tar all theses files into an archive 20?? _ ...
1
vote
1answer
174 views

`tar` with `find` with removing original file extension

I want to create tb2 files from bunch of text files like this. tar cfj $(basename ./2014_04_09.txt .txt).tb2 $(basename ./2014_04_09.txt) With this command I can create a archive file 2014_04_09.tb2 ...
3
votes
5answers
2k views

Formatting the output: Underlining

I wrote the following function in ksh that prints its first argument to the screen and underlines it with the appropriate ammount of - character: print_underlined () { word=$1 echo $word ...
3
votes
1answer
106 views

Merging text files based on their filename

I have hundred of files with the following format: 2013_01_19_xyxyxyx.txt 2013_01_19_xyxyxyx.txt 2014_03_21_xyxyxyx.txt 2014_03_21_zxzxzxz.txt 2014_03_22_abababa.txt 2014_03_22_cbcbcbc.txt etc. I ...
1
vote
0answers
77 views

Execute commands on TMUX Detach

Is it possible to execute commands on tmux detach? I usually have a rails console and server running in the tmux session, on detach is it possible to automatically end those? Thanks.
0
votes
3answers
671 views

Proper place to put shell prompt(PS1) when use sh/bash/zsh together

I'm using dash(sh) or bash or zsh. If possible, I would prefer to put in common place. I want to put proper PS1 settings when I interactive with shell, so these situation should be considered login ...
7
votes
5answers
588 views

copy smallest files first?

I have a large directory containing subdirectories and files that I wish to copy recursively. Is there any way to tell cp that it should perform the copy operation in order of file size, so that the ...
8
votes
3answers
2k views

/bin /etc /lib64 /root /sbin deleted or moved by mv folder/* /* while su

OS is Centos 6.5 64-bit I downloaded a tar file and wanted to untar and mv it. I untared, then accidentally (as root) ran mv folder/* /* instead of mv folder/* . bash said it couldn't overwrite some ...
2
votes
1answer
152 views

What is the ` character or symbol called and what is its significance outside of SE code formatting? [duplicate]

What is the ` character's name and what is its significance outside of SE code formatting because I cannot get it to work? I'm familiar with its use in the Stack Exchange forums used to format code ...
5
votes
1answer
6k views

Why is my find not recursive?

I am running the following command, but it is not performed recursively: find . -name *.java I know there are java files further down in the current directory but it is performing the find on the ...
2
votes
4answers
113 views

Can a running script identify the logging context?

Let us say I redirect the STDOUT, STDERR of a program to files. ./script.sh 1> output.log 2> error.log Can the running program find this out i.e. know the paths to these files?
2
votes
2answers
236 views

Linux Shell fundamentals: How can I check the file descriptors status, (where are redirected to) right now without lsof?

I am learning about file descriptors for the case of Linux, and I was wondering if there is any command showing a complete list that allows me to know where is each one redirected to in this moment. ...
1
vote
1answer
617 views

How to trace system calls being invoked after typing command?

This question is relevant to the question of 'what happens when we type a simple command on shell?' I posted earlier. (I thought it would be better to post it seperately. But if not, please let me ...
2
votes
1answer
105 views

Accidentally typed crontab with just the dash

What happens when I type just "crontab -"? The "e" didn't take before I hit Enter. It just moved the cursor to the next line and I had to Ctrl+C to exit, but I'm not sure what it did exactly. I'm on ...
8
votes
2answers
264 views

How do I elevate privileges in the middle of pipeline?

My guess was as follows: echo "Generating some text" | su - -c cat >/output/file But su says: su: must be run from a terminal What would you do?
16
votes
2answers
1k views

What happens when we type a simple command on shell? [duplicate]

I have a simple doubt on execution of a simple command. As per my understanding, when we type a command such as ls on interactive shell, Shell interpretes the command. Shell creates a child process ...
6
votes
3answers
412 views

Understanding environmental variables in different contexts

Trying to understand the behaviour of the environment in Linux (Ubuntu 13.04 concretely), I've find different situations where setting envirionment variables are used or defined for/in different ...
3
votes
2answers
592 views

Passing arguments to su-provided shell

man su says: You can use the -- argument to separate su options from the arguments supplied to the shell. man bash says: -- A -- signals the end of options and disables further option ...
3
votes
1answer
7k views

Bash command not found error

Why would the following script give following errors : ./check1.sh: line 10: Hi,: command not found ./check1.sh: line 21: syntax error: unexpected end of file check1.sh: #!/bin/bash subj="host ...
1
vote
1answer
78 views

Is there an advantage in using ksh over zsh? [closed]

Or are there any advantages for using ksh over zsh? Would any specific commands not execute successfully across the shells or are the major differences not command related, but something else?
22
votes
5answers
7k views

How to make bidirectional pipe between two programs?

Everyone knows how to make unidirectional pipe between two programs (bind stdout of first one and stdin of second one): first | second. But how to make bidirectional pipe, i.e. cross-bind stdin and ...
4
votes
3answers
2k views

How to use a variable as part of an array name

I have two arrays: arrayA=(1 2 3) arrayB=(a b c) and I want to print out one of them using a command line argument, i.e., without any if else. I tried a few variations on the syntax with no ...
9
votes
3answers
11k views

What does $# mean in shell?

What does $# mean in shell? I have code such as if [ $# -eq 0 ] then I want to understand what $# means, but Google search is very bad for searching these kinds of things.
4
votes
3answers
353 views

What's the right way to set “dynamic” PATH in bash? (for android sdk)

I have android sdk installed, and I want the binaries in build-tools/android-VERSION to be available in PATH, so I add few lines: ...
2
votes
3answers
1k views

How to run a script after connected with ssh

I've heard multiple answers of rights and wrongs and I still don't know if its possible. I ssh to a server then want to run a block of script. while read server <&3; do #read server names ...
1
vote
2answers
34 views

Install-on-Demand Wrapper Function for Executables

How do I make the following function work correctly # Install git on demand function git() { if ! type git &> /dev/null; then sudo $APT install git; fi git $*; } by making git $* ...
4
votes
3answers
924 views

Find files that have words in common

What would be the best way to create a list of files that have common words with a given file. For example, if I had: $ ls mainFile file1 file2 file file4 $ cat mainFile exquisite malicious ...
5
votes
4answers
1k views

Run a command when system is idle and when is active again

I want to run a command when the user becomes inactive (the system is idle). For example: echo "You started to be inactive." Also, when the user becomes active again (the system is not idle ...
1
vote
3answers
713 views

`wait` doesn't wait for `wget --background`

I have gone through several SE posts on the unix wait command and none of the posts resolve my problem. I have a weather forecast model to run. It has first to prepare some folders, then download data ...
5
votes
2answers
127 views

Command substitution vs I/O Redirection?

I am wondered about differences between I/O Redirection and Command substitution? For example when I want to redirect which command output to cd command (I know that it's not a directory) then the ...