The shell is unix's command-line interface. You can type commands in a shell interactively, or write scripts to automate tasks.

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3
votes
2answers
28 views

How do I break up a file like split to stdout for piping to a command?

I have a large .sql file full of SELECT statements that contain data I want to insert into my SQL Server database. I'm looking for how I could basically take the file's contents, 100 lines at a time, ...
3
votes
2answers
116 views

How can I print out all but the last n characters in bash?

I'm working with standard input (cating two files together) and want all but the last 10 characters of the result to be passed through the next command. All I can find through searching is using sed, ...
6
votes
2answers
217 views

In an empty environment, how are executables found?

For experimentation purposes I created a binary that prints the $PATH, and calls which as follows: #include <stdlib.h> #include <stdio.h> int main() { char *path = getenv("PATH"); ...
4
votes
3answers
95 views

Dynamically trim stdout line width in Bash

Lately, I have been experimenting with the ps command, and sometimes long paths wrap to the next line (or two) and make it hard to read. I want to pipe the ps output into another program to limit the ...
1
vote
1answer
60 views

Best way to determine piped command to shell script?

Given tree /some/directory | print.sh Is there any way for print.sh to know that "tree -f /some/directory" was called, without trying to parse pid processes?
3
votes
5answers
2k views

What does exit 99 means?

I'm new to Unix. Just want to know what is exit 99 and why would one use it and what are the significance uses of it. For example, I'm using exit 99.
0
votes
2answers
41 views

ln -s with a path relative to pwd

I'm trying to create a bunch of symbolic links, but I can't figure out why this is working ln -s /Users/niels/something/foo ~/bin/foo_link while this cd /Users/niels/something ln -s foo ...
16
votes
7answers
447 views

How do I source another process's environment variables?

If I examine /proc/1/environ I can see a null-byte-delimited string of process 1's environment variables. I'd like to bring these variables into my current environment. Is there an easy way to do ...
3
votes
3answers
134 views

Rescue value from second last line

After I run a script, I've got the following lines: PyMOL(TM) Molecular Graphics System, Version 1.4.1. Copyright (c) Schrodinger, LLC. All Rights Reserved. Created by Warren L. DeLano, ...
7
votes
6answers
602 views

Is it possible to remove folder prefix from a `ls` command

I am in a bash script and I want to get the list of all files (let say all jar files). I execute the command ls -1 lib/*.jar and I get the output: lib/mylib_1.jar lib/mylib_2.jar ... Is there any ...
6
votes
1answer
89 views

How to specify additional parameters for GNU sort's --compress-program option?

sort --compress-program=/bin/gzip works fine, but how can I pass options down to the compression programm (e.g. --best or --fast)? sort --compress-program=/bin/gzip\ --best failes with the error ...
1
vote
1answer
25 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
35 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 ...
24
votes
5answers
1k views

How does clear command work?

I was recently trying to learn more about how the shell works and was looking at how the clear command works. The executable is located in /usr/bin/clear and it seems to print out a bunch of blank ...
0
votes
2answers
71 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 ...
4
votes
5answers
99 views

`ls -l` of a file and all the directories leading to it?

Before I start writing a (probably easy) script, is there a command that does the equivalent of the following one: [:~/software/scripts] % ls -ld / /usr /usr/bin /usr/bin/tee drwxr-xr-x 21 root root ...
0
votes
0answers
11 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?
5
votes
3answers
399 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 ...
1
vote
2answers
43 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 ...
3
votes
1answer
41 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
1answer
43 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: ...
10
votes
6answers
503 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 ...
8
votes
4answers
215 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
14 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
22 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 ...
1
vote
1answer
60 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 ...
1
vote
3answers
65 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 ...
5
votes
2answers
202 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 ...
2
votes
1answer
31 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 ...
3
votes
2answers
148 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 ...
13
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 ...
7
votes
5answers
315 views

How to extract logs between two time stamps

I want to extract all logs between two timestamps. Some lines may not have the timestamp, but I want those lines also. In short, I want every line that falls under two time stamps. My log structure ...
1
vote
2answers
29 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?? _ ...
3
votes
1answer
29 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
17 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.
1
vote
1answer
33 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 ...
78
votes
3answers
7k views

Why is “echo” so much faster than “touch”?

I'm trying to update the timestamp to the current time on all of the xml files in my directory (recursively). I'm using Mac OSX 10.8.5. On about 300,000 files, the following echo command takes 10 ...
7
votes
5answers
475 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 ...
16
votes
6answers
2k views

Why do I have to cd out of a deleted directory?

On my server I have a directory structure looking something like this: /myproject/code I normally have an ssh connection to the server and 'stand' in that directory: root@machine:/myproject/code# ...
2
votes
1answer
50 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 ...
2
votes
4answers
72 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?
1
vote
1answer
61 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 ...
14
votes
2answers
740 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 ...
3
votes
1answer
125 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
2answers
77 views

Close all file descriptors in bash

Is there a way to close all the open file descriptors, without having an explicit list of them beforehand?
0
votes
2answers
34 views

command condition sometimes integer sometimes string

I want to execute this condition while [ $(cat /path_of a file/) -eq 1 ] The condition is only correct if $(cat /path_of a file/) is an integer and not a string ! How can I overcome this ...
5
votes
3answers
181 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 ...
8
votes
3answers
526 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
110 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
52 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?