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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5
votes
2answers
457 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 < ...
2
votes
3answers
245 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 ...
4
votes
1answer
4k 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
votes
1answer
467 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 ...
21
votes
4answers
816 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
181 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
votes
1answer
37 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
34 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
20 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
votes
6answers
260 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
vote
2answers
41 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
votes
0answers
757 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 ...
3
votes
1answer
43 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
vote
3answers
78 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
votes
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 ...
0
votes
2answers
78 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
votes
4answers
181 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
vote
3answers
89 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
66 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
vote
2answers
51 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
79 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
680 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
votes
1answer
50 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
votes
1answer
40 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
vote
0answers
32 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
199 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
111 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
vote
2answers
114 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
66 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
296 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
83 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?
-3
votes
2answers
33 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)
8
votes
4answers
1k 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: ...
0
votes
3answers
60 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 ...
0
votes
2answers
57 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
votes
3answers
522 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
101 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
votes
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
94 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 ...
1
vote
1answer
40 views

How to assign words with spaces as a whole name to variable in shell script? [duplicate]

I need to make some directory of Author name. It's easy when doing them alone. I can simply mkdir "Mario Luis Garcia" This will create one directory named "Mario Luis Garcia" But when trying do it ...
4
votes
1answer
583 views

command: ls /etc | sort | grep d* is yielding no results but ls /etc | sort | grep p* lists entire directory

I am playing around with piping and grep tonight. I know that grep uses regex and that * means 0 or more occurrences of the preceding character. So the way I understand it is that if I do the ...
8
votes
4answers
1k views

Why is the 'if [ $1=“1” ]' branch always selected even if $1 is not 1?

I have a shell script named 'teleport.sh' like this: if [ $1="1" ]; then shift mv "$@" ~/lab/Sun elif [ $1="2" ]; then shift mv "$@" ~/lab/Moon elif [ $1="3" ]; ...
1
vote
1answer
36 views

Can you further integrate and present sequential moreutils vipe command output in vim using successive splits etc?

I have used the moreutils suite a few times and I find it makes you think further about base utilities and is insightful(and fun). For instance, vipe allows running an editor - like vim - in the ...
0
votes
2answers
204 views

Getting expr: syntax error on index [duplicate]

Using this OF=$(ps fax | grep 'php-fpm: master process' | awk '{print $1}') IDX=`expr index $OF ' '` I get an error. The results of the $OF variable are: 27797 27495 What is the error here? I ...
3
votes
1answer
35 views

Can I make “less” execute arbitrary commands with a single key sequence?

The crux of my question is stated in the title. Reading the less and lesskeys manpages, I have created a file containing: ^B shell touch ~/testfile and run it through lesskey to generate ...
12
votes
3answers
831 views

How to undo `set -x`?

I typed set -x in terminal. Now the terminal keeps printing the last command run on top of my output so the command ~]$echo "this is what I see" returns + echo 'this is what I see' this is what ...
2
votes
1answer
72 views

Why does `cp -a . /dir` copy contents instead of directory?

I wanted to copy a directory that I was presently in. I tried cp -a . ~/xyz It copied the contents of the directory, yet this worked: cp -a "$(pwd)" ~/xyz [As desired, this copied the directory ...
1
vote
3answers
226 views

Why is ls command slow to interrupt on NFS directory with lots of files?

I noticed in directories with lots of files on NFS if I do ls * then hit Ctrl-C it can take a while ( say 20 seconds ) before ls comes back. Why? Can ls command be fixed to be more responsive?