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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103 views

I want to suppress “no access to tty” error message?

I have a bash script where I use ssh to connect to another server and run some commands there. I found some sites that the error (Warning: no access to tty (Bad file descriptor). Thus no job control ...
8
votes
1answer
235 views

How to “correctly” start an application from a shell

I find it hard to phrase the question precisely but I will give my best. I use dwm as my default window manager and dmenu as my application launcher. I hardly use GUI applications aside from my ...
2
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0answers
55 views

How can you get the current terminal line (the one that is still editable by the user)?

I need a way to use the current line which the users typed into as variable for a shell function. my current code, which can be called by ctrl+r zle -N search bindkey "^R" search search () { read ...
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2answers
44 views

Passing print pattern as a variable to awk

I am trying to use awk to print variables from various columns in a line delimited by , .The columns and pattern which I want to print is stored in another variable b. The pattern a and print patter ...
1
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1answer
119 views

Pattern replacement

Please can anyone explain to me in brief the syntax of this command. Explanation in terms of how actually this command is written significance of each and every character used. I know the output of ...
0
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2answers
104 views

Login by ssh , exec one command and i don't want to quit the bash

I want to change PS1 when i ssh another centos strshell = 'PS1="remote!"' os.system("ssh -i %s -l%s -p%s %s %s"%(SSH_KEY,SSH_USER,SSH_PORT,des,strshell)) ssh quit automatically. I want to ...
1
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2answers
61 views

Confusions mitigation while working similar environments in multiple servers

I often have to open multiple ssh sell terminals of remote servers together., eg. Dev and test. These paths and applications are exactly similar. And I am often confused if I run a particular command ...
2
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2answers
50 views

How do you get a count of all file extensions on a hard drive using the gnu+linux terminal?

On windows I have a program that can count all the files on a hard drive and the output shows a list of file extensions and a number (which showed how many files on the drive were for example are ...
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2answers
442 views

Is there any way to read lines from command output?

I have a pre process command to output a file ./preprocess.sh > preprocessed_file and the preprocessed_file will be used like this while read line do ./research.sh $line & done < ...
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0answers
16 views

Explain a tsums command line

In putty, I am blindly writing codes as below, cat >! lot tsums @lot -format=lot,machine_id > ! MCID what is the meaning of these 2 lines?
2
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3answers
150 views

Saving individual output lines into variables

I'm using find -mtime -2 to find files modified in the past 24 hours or less. The output looks like this. /home/user/logs/file-2014-08-22.log /home/user/logs/file-2014-08-23.log I need to save the ...
2
votes
1answer
897 views

Syntax error near unexpected token `('

When I use below code in SSH terminal for CentOS it works fine: paste <(printf "%s\n" "TOP") But if I place the same line code in a shell script (test.sh) and run shell script from terminal, it ...
2
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1answer
234 views

Running sh script: «Permission denied» despite the executable bit and root rights

I installed Debian in VirtualBox (for various experiments which usually broke my system) and tried to launch the VirtualBox guest addon script. I logged in as root and tried to launch autorun.sh, but ...
20
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4answers
784 views

Why doesn't the tilde (~) expand inside double quotes?

According to this answer and my own understanding, the tilde expands to the home directory: ➜ ~ echo ~ /home/braiam Now, whenever I want the shell expansion to work, i. e. using variable names ...
3
votes
4answers
153 views

gunzip a folder with many files

I have a folder with 36,348 files gz files. I want to unzip all of them. Running: gunzip ./* results in -bash: /usr/bin/gunzip: Argument list too long Whats the easiest way to get around ...
2
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1answer
23 views

ionCube shell script gives error

I have this shell script to install ionCube loader: if [[ $(id -u) -ne 0 ]] ; then echo "Please run as root" ; exit 1 ; fi echo "Welcome to this script to install the ionCube loader on CentOS!" cd ...
5
votes
1answer
27 views

Upstart and bash function names containing “-”

I inherited some bash scripts where the author used "-" in the function names instead of the more normal "_" e.g.: function a-b { ... } Ugly but legal in bash. Problem is I sourced this inside an ...
2
votes
1answer
18 views

Comparison of columns in two files and appending the first file

I need a help on this :- I have a file : emp.txt 21356 suresh 12/12/2012 23511 ramesh 11/06/2011 31456 biswajit 09/08/2013 53134 archan 06/02/2009 first field:- employee id, 2nd field is name and ...
8
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6answers
240 views

Obtain values of a section of a file

I have a configuration file in the following format. <Title> [part1] A.File = a A.Val = val1 B.File = a B.Val = val1 [part2] A.File = a1 A.Val = val2 B.File = a B.Val = val1 ...
1
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2answers
37 views

How do I find a files directory?

I am looking for a specific file in OS/X. I can see the file by using: ls -alR | grep "mkmf.*" This shows my that the file exists. How do I find what directory the file is located. Many thanks ...
13
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0answers
756 views

What does “mv *” do? [duplicate]

I just gave this command by accident mv * while I was in a directory, needless to say that the content of my dir is gone and I have almost no hope to recover it, luckily it wasn't something ...
2
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1answer
36 views

Read target of symlink and increment target by one

I have a folder structure that looks like this /some/folder/1 /some/folder/2 ... and a symlink current that links to one of the folders. Is it possible and when how to read the target of the link, ...
1
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3answers
51 views

How to send a output of unix command from one server to another server?

How to redirect the output of a unix command from one server to another server. I should be able to send the unix command's output from server-1. Then I should be able to receive the output in ...
4
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2answers
64 views

How do I cancel/replace one element of running `cmd1 && cmd2 && cmd3 && …` chain?

$ command1 && command2 && command3 Running command1 ... Running command2 ...^Z [1]+ Stopped $ fg && command4 && wrong_command5 && command6 Running command3 ...
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2answers
47 views

How to set cron job for system

I'm really new on Linux and have no any previous experience on it. And I opened this account to ask this question. I need to install a cron job I've followed the short guide here. Well, I think it ...
3
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4answers
164 views

Redirect and pipe output

rpm -qa > file | wc -l returns 0. What am I doing wrong? I think it is clear what my goal is, but it isn't working. Is this a job for xargs or tee?
1
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3answers
53 views

How to handle backspace while reading?

How do I handle the backspaces entered, it shows ^? if tried & how read counts the characters, as in 12^?3 already 5 characters were complete(though all of them were not actual input), but after ...
1
vote
3answers
48 views

bash/shell pathname expansion for mkdir, touch etc?

So doing something like this in bash and most other shells won't work to create multiple subdirectories or files within subdirectories... mkdir */test touch */hello.txt There are of course many ...
1
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2answers
41 views

Why asterisk in command result in for loop is expanding?

I want to write a script that will run git diff --name-status master..<BRANCH> but when I run this: for i in $(git branch | grep -v master); do echo $i; done I get echo one directory ...
3
votes
6answers
76 views

Use a shell not installed on remote machine

Given the scenario: Remote machine: SSH server; user does not have admin privileges; Local machine: SSH client; user has admin privileges. If user, logging in to remote from local, wishes to ...
9
votes
3answers
664 views

What is the usage of $& in bash?

I was looking into special parameters in bash. I am curious to know what is $& and how it is different from $_. I see the following output when running the commands but could not locate the ...
0
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1answer
45 views

`command` vs `type` - Locate program file in user's PATH [duplicate]

I need locate program file in user's PATH. I found few solution, the best are command and type. Which is better, faster, UNIX-like way and why? command -v <application> type -p ...
0
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1answer
37 views

Quote escaping struggle with grep and sed

I'm writing a bash script to extract data from html tags and I found this command in another thread : grep -o '<tr>.*</tr>' HTMLFILE | sed 's/\(<tr>\|<\/tr>\)//g' > NEWFILE, ...
1
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0answers
31 views

Edit a command? [duplicate]

I'm using many basic commands of unix/linux. In Mac OS X Mavericks, I type cat for a file, but output was faulty. In example, content of the file named bar: foo bar Then: ...
3
votes
1answer
180 views

How does the colon sign and dollar question mark combine in sh?

The "colon sign" and the "dollar question mark" can be combined to check if a sh script does have an argument and assigns it directly to a variable of interest: cmd=${1:? "Usage: $0 ...
3
votes
1answer
24 views

X commands do not start from my at job

I'm learning about Linux scheduling commands including at, cron, sleep etc. I'm trying to launch gedit after x minutes via the at command. This is what I have: kedar@i5 ~ $ at now + 1 minute at now + ...
4
votes
3answers
100 views

Passing arguments from one command into the next

I'm trying to write a script to unify two separate commands I run by hand into a single bash script I can then cron. The first command is a simple find on files with a certain name and size find ...
1
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2answers
101 views

Rename a file dynamically containing spaces [duplicate]

I want to rename a file dynamically based on data which contains spaces Name="Abc DEF" Name1="GHI JKL" mv /sample/pdf/noriginalName.pdf /sample/outputPdf/${NAME}${Name1}".pdf" But it gives me an ...
4
votes
2answers
51 views

Inconsistent redirection behavior ssh interactive vs commands

These work, ssh remote 'echo hi > hi.txt' echo hi | ssh remote 'cat > hi.txt' but this does not work ssh remote sh -c 'echo hi > hi.txt' I expected to produce a file on remote named ...
4
votes
6answers
290 views

want the last line when duplicate awk?

I have the file: key value blah blah blah blah blahblah man1 boy1 blah blah man1 boy2 man1 boy1 I do this to remove duplicate lines: awk '/man1/ { print $1,$2} ' file | awk '!x[$0]++' and the ...
1
vote
1answer
30 views

How to delete older files in a folder in unix?

Can anyone help me find the meaning of the below statement? I am new to Unix programming. find /sourcedirectory -mtime +2 -exec mv "{}" /destination/directory/ \;
16
votes
5answers
1k views

Parenthesis in bash arithmetic: 3 * (2 + 1)

expr does not seem to like parenthesis (used in mathematics to explicit operator priority): expr 3 * (2 + 1) bash: syntax error near unexpected token `(' How to express operator priority in bash?
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votes
2answers
29 views

how to take the file names from folder

i want to write a program for the below logic: Take the names of files in a folder For each file: print file name move the file to another new folder (with the name in dd_mm_yy format)
6
votes
4answers
470 views

Send SIGINT to child process of shell, simulating CTRL+C (Linux)

Given a shell process (e.g. sh) and it's child process (e.g. cat), how to simulate the behavior of CTRL+C using the shell's process ID? This is what I've tried: Running sh and then cat: ...
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3answers
42 views

store the command output in an array and print one by one

This is my command: cat httpd.conf | grep ^LogFormat | awk -F\" '{print $(NF)}' Output of this: commonsess common or can be any number of values, I need to store these values in an array and ...
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2answers
42 views

Command substitution in Shell Script

511@ubuntu:~/Unix$ cat pass hellounix file1 #!/usr/bin echo "Enter File Name" read file if [ -f $file ] then echo "File Found with a Name $file\n" echo "File Content as below\n" count=0 ...
5
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3answers
270 views

Sorting ls output by time, when there are too many files for a single invocation

I know that I can sort the output of ls by time with the -t option. I know that when I have so many files that they don't fit in a single ls invocation, I can normally use xargs (or find ... -exec ...
0
votes
3answers
96 views

What does running “< ./somefile.txt” in shell do?

So I just executed < ./somefile.txt in a shell, and it doesn't appear to do anything (the text file has valid linux commands). So where are the contents of the text file being redirected to? I'm ...
0
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0answers
24 views

How to make the process run after closing the session [duplicate]

I have started a process in Linux without a terminal multiplexer like screen or tmux, without nohup. Now I want to logout from my remote ssh session without interrupting the execution of that process. ...
0
votes
1answer
64 views

Backing up files which were modified after the last backup was run

I am working on a backup script (bash shell - Fedora - VMware) that should compare a file with last modified attribute and current date and should back it up if the last modified date is older than ...