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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3
votes
3answers
110 views

Shell test to find a pattern in a string

I just wanted to ask whether there is any command which would work on common shells (bash, dash, kornshell)? It is supposed to check if the line variable contains any part of the path. if [[ $line =~ ...
2
votes
4answers
1k views

Get the latest directory (not the latest file)

My folder parent has the following content: A.Folder B.Folder C.File It has both folders and files inside. B.Folder is newer. Now I just want to get B.Folder, how could I achieve this? I tried ...
3
votes
2answers
2k views

chmod + silent mode + how force exit code 0 in spite of error

Is it possible execute chmod and ignore error from command Example ( remark file.txt not exsist to show the example ) When I type chmod 777 file.txt I get error on the output chmod: cannot ...
2
votes
3answers
177 views

Double square brackets for FreeBSD

I have this code: [[ "$1" =~ [/\\]$ ]] On linux it works just fine, but when I tested it on FreeBSD an error occured : ./projekt2.sh: [[: not found and it .. I there any alternative which would ...
21
votes
7answers
1k views

`command .*` acts on the parent directory

Someone of our team wanted to recursively change the user permissions on all hidden directories in a users home directory. To do so he executed the following command: cd /home/username chown -R ...
2
votes
1answer
27 views

How do I run two processes and find out when one ends in bash

I was thinking to do something like this: command1 & command2 wait Will this work? I want to proceed when command2 finishes, but command1 can still be running.
1
vote
1answer
37 views

How to interactively remove all directories matching given criteria?

My script below has two problems: The script stops after first matched directory rm -i is not quite interactive What are my incorrect assumptions that make it fail? How can I fix it? ls -1A | ...
1
vote
2answers
51 views

pipe in shell with redirection

My understanding is that a pipe in shell like a | b redirects b's stdin to a's stdout. However, I tried ls | less < somefile, the behavior is very strange. less shows the output of ls concatenated ...
0
votes
0answers
60 views

Backup And Restore Shell Script

I have been trying to create a script that backups up a certain directory and then restores the directory. The backup works as it should but when I try run the restore function I get the following ...
3
votes
2answers
5k views

Exporting a variable with dot (.) in it

How to export a variable which has dot in it. I get 'invalid variable name' when I tried : export my.home=/tmp/someDir -ksh: my.home=/tmp/someDir: invalid variable name Even escaping metacharacter ...
-1
votes
2answers
25 views

Create new file with spaces from argument BASH [duplicate]

I need to create new file which contains spaces in it. And it is passed through the argument. This code below creates 2 sepate files. Can anyone help me how to create 1 file which will contains space? ...
19
votes
2answers
430 views

Where is “export var=value” not available?

I have picked up -- probably on Usenet in the mid-1990s (!) -- that the construct export var=value is a Bashism, and that the portable expression is var=value export var I have been advocating ...
2
votes
2answers
39 views

Porting Linux date parsing to FreeBSD

I have date in this format: date -d $datum +"%Y-%m-%d" and on Linux it worked OK but in FreeBSD says this: ERROR wrong format usage: date [-jnRu] [-d dst] [-r seconds] [-t west] [-v[+|-]val[ymwdHMS]] ...
0
votes
1answer
49 views

SHELL— Date format validation

How can I check whether the format of date is correct without date command being printed? date -d $datum +"%Y-%m-%d" if [ $? -ne 0 ] ;then echo error exit fi
1
vote
2answers
6k views

How to fix “login: no shell: No such file or directory” when I can not even login?

I installed fishfish(a user-friendly interactive command line shell) on a Linux server, later somebody uninstalled it but I don't know it. After I run chsh -s /usr/local/bin/fish without caution, I ...
1
vote
1answer
53 views

SHELL regular expression ends with backslash

I want to check if the pattern ends with "/" or "\" and before it can be any string. I tried this *\/ * for any string, \ for removing meaning of "/" and / for "/"
0
votes
2answers
51 views

What is the variable of $#?

I'm learning introductory Linux and came across something which I did not understand: "The following command has been executed: set 10 20 30 40 50 Enter the value of the variable $#: I understand ...
1
vote
1answer
758 views

Adding multiple user with shell script on Ubuntu

Can someone help me in providing me the shell script for creating multiple users on Ubuntu. Password needs to be different for each user. Thanks in advance
1
vote
0answers
23 views

How do processes, jobs and session relate to each other ? [duplicate]

Could you deliver an answer in a way that does not require too much special knowledge in advance, yet also deliver some deeper insight to a lesser advanced Linux User ?
9
votes
1answer
712 views

What exactly is scrollback and scrollback buffer?

What are "scrollback" and "scrollback buffer" in programs like bash and screen, and how do they relate to the tty, the programs being run, and stdin/ stdout/ stderr? Here is the only definition of ...
2
votes
2answers
71 views

Print file contents and delete the printed content* from the file

In Linux, from a bash shell, how can I print the contents of a file and remove the content I just printed content from the file? I have a program writing texts to a file repeatedly. On a Linux shell ...
0
votes
1answer
49 views

Shell— print only certain lines from output

I need to choose from output only lines where number is bigger than chosen number. For example x=27 and I need to find only lines where the number in first column is bigger than that x. In this ...
0
votes
0answers
42 views

Shell splitting line into words without temporary file

yesterday I found out that this creates temporary file. Can anyone help me how to rewrite it so it wouldn't? I am desperate I have tried everything that I know, but it doesn't want to work. And also I ...
0
votes
0answers
50 views

Restrict FTP user to access only its own directory and Download Only

I need to create a user which can only FTP to specific directory and download data from it only no upload or delete files. After searching on line I reached to following points useradd -g 10 -d ...
8
votes
4answers
2k views

how can a makefile detect whether a command is available in the local machine?

I began to use org-mode for planning out my tasks in GTD-style system. Putting every org files in a directory of a Dropbox folder, I run emacs to edit / manage these files from three different local ...
2
votes
3answers
63 views

What happens if I pass too few parameters to a shell function?

I would like to ask about passing parameters into functions. I tried this: function_name $var1 $var2 but usually (sometimes it printed error) it didn't make any difference whether I passed them or ...
2
votes
3answers
42 views

Command substitutions vs backslash escapes in a quoted string

Consider a double-quoted command substitution with backslash escapes inside it, like this: echo "$(echo '\\')" It prints out \\, whereas I would have expected it to print out only one backslash. My ...
0
votes
1answer
52 views

can we get sorted grep output

I have same: 1.txt with apple written in it, 2.txt with mango written in it, 3.txt with apple written in it, 4.txt with mango written in it. grep -e apple -e mango *.txt will give result as: 1.txt: ...
13
votes
1answer
7k views

touch: cannot touch `foo': No such file or directory

What could cause touch to fail with this error message? touch: cannot touch `foo': No such file or directory Note that an error due to incorrect permissions looks different: touch: cannot touch ...
3
votes
1answer
26 views

Trailing colons and dash's builtin test command

What's the meaning of a trailing colon to dash's builtin test (or [) command? I was surprised when I found that if [ ... ]: ; then .. ; fi works (at all) in dash, but not bash, and it seems to be ...
-3
votes
0answers
33 views

Convert file pattern in Unix

I have a file with content as below 31/01/2014 1234 2234 4567 3321 ...n Need to write a shell script to convert the above file as below: DD_Date='31/01/2014' ...
6
votes
1answer
825 views

What is the meaning of 'ln -sf' in Linux?

I have 2 questions. First one is for the -sf options and second one is for the more specific usage of -f options. By googling, I figured out the description of command ln, option -s and -f. (copy ...
1
vote
2answers
55 views

Remove paragraph from file

I have a file (file.php) like this: ... Match user foo ChrootDirectory /NAS/foo.info/ ForceCommand internal-sftp AllowTcpForwarding no GatewayPorts no ...
1
vote
1answer
24 views

Switch-case block inside define keyword in a single logical line in a makefile

This is the code excerpt from ghc.mk, part of Haskell source compilation. I find it different, because the author has chosen to write one function block in a single line. Is it a common practice in ...
1
vote
1answer
61 views

Brace expansion not working in a script

for i in {1..40} do echo $i done I got {1..40} and I would like to have something like 1 2 3 and so on so I can use the variable i inside a command's parameter.
28
votes
4answers
2k views

Why do many commands provide a “quiet” option?

Why do many commands provide the option -q or --quiet to suppress output when you can easily achieve the same thing by redirecting standard output to the null file?
0
votes
1answer
41 views

How do i write a shell script so that when i compile my c++ program it will put the binary into the Binary Directory

I have a directory called Binary and bunch of source files: ./ ├── Binary/ ├── lesson02.cpp ├── lesson04.cpp └── lesson06.cpp when I compile the source code g++ lesson01.cpp -o lesson01 I want ...
0
votes
4answers
70 views

Copy same specific parts of a file to another file

How can I copy same specific parts of a file to another file? In the first file, I have: user01: Id name nationality user02: Id name nationality . . . I want to copy each piece of information to a ...
9
votes
3answers
4k views

Using notify-send with cron

I am using Arch Linux with KDE/Awesome WM. I am trying to get notify-send to work with cron. I have tried setting DISPLAY/XAUTHORITY variables, and running notify-send with "sudo -u", all without ...
10
votes
3answers
12k views

Understanding backtick (`)

I am trying out the command $ b=5; echo `$b`; -bash: 5: command not found but it does not print 5 as it is supposed to. What am I missing here? What does ` (backquote/backtick) mean in bash? seems ...
5
votes
3answers
275 views

How to put a newline special character into a file using the echo command and redirection operator?

I would like to create a file by using the echo command and the redirection operator, the file should be made of a few lines. I tried to include a newline by "\n" inside the string: echo "first ...
2
votes
1answer
45 views

How to verify the target of a symbolic link points toward a particular path

Within a bash script, I know I can check if a file is a symbolic link with the following syntax if [ -L $path ] Does any one know how I would test if that path was linked to a particular path? E.g. ...
-1
votes
1answer
31 views

Mutiple commands after sudo in one line

I want to execute multiple commands after a sudo command su - appuser -c "cd /apps/bundle/bundle-client/bin ; export BDL_WEB_USER=not_used ; export BDL_WEB_PASSWORD=not_used ; ./bundle -b ...
0
votes
0answers
41 views

How to get and print a user's public IP address in a Shell Script? [duplicate]

I've just completed a lengthy installation script that deploys a Ruby on Rails application unto web servers. At the end of this script, I'd like it to print something along the lines of: "Installation ...
4
votes
1answer
58 views

Why does 'jobs' always return a line for finished processes when run in a subshell within a script?

Normally, when a job is launched in the background, jobs will report that it is finished the first time it is run after the job's completion, and nothing for subsequent executions: $ ping -c 4 ...
1
vote
1answer
47 views

Search for text inside java command output

I have a folder which have multiple Jar files. * dummy.jar * myjar-xx.jar * myjar-yy.jar Using find, I need to find first file starting with "myjar" Now, I want to grep the contents of ...
1
vote
1answer
36 views

How do I run a program without network access? [duplicate]

I am making a program that scrapes information from some web services. I want to test how my program reacts when it can't reach the web service, like if the web service is down or if the local ...
3
votes
2answers
45 views

Shell globbing without matching files

I frequently make use of shell file name globbing to do things like operate on all of /dev/sda, /dev/sdb, /dev/sdc, etc by doing /dev/sd[a-f], however, this relies on there being files on disk that ...
0
votes
1answer
50 views

Can a command in a shell pipeline determine the tty characteristics of its context?

I have a bash script that columnizes a list of items. By default it will guess at the number of columns to output, based on the terminal width as reported by stty size. But when the script is in a ...
1
vote
4answers
92 views

How do I suppress error messages from cp?

I am currently looking ways to suppress error command in Linux, in particular, the command cp. I do: root@ubuntu:~$ cp /srv/ftp/201*/wha*/*.jj ~/. cp: cannot stat `/srv/ftp/201*/wha*/*.jj': No ...