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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Why are UNIX shells like this and how can I work around it?

One of the things I've noticed about BASH and other UNIX shells is that, by default and when used in typical ways, they spawn subshells for almost everything. e.g. foo=$(grep "someword" ...
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3answers
15 views

Shell pattern matching vs. regular expressions occurence

I am relatively new to Unix, and I stumbled across one curiosity. Some shell constructs like case or find, employ pattern matching, but it is not quite regex. Other commands, like ed, sed, vi, and ...
-18
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3answers
187 views

Which amongst the given option is TRUE about login shell?

Which amongst the given option is TRUE about the login shell? The login shell varies every time the user logs in. The kernel decides on the availability of the shell during login. The login shell ...
0
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1answer
24 views

Changing my default directory in passwd changes my prompt

I don't understand what's happening in this scenario. I changed the home directory of a user by editing the /etc/passwd file instead of using usermod -d. It worked: the default directory wasn't ...
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2answers
21 views

List of subdirectories that contains a particular file name

I am wondering if i can do this in a single shell command. I am in home directory and want to find a list of subdirectories that contains a particular file. The file name and the depth is always ...
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4answers
3k views

Convert linux sysuptime to well format date

I want to display /proc/uptime in well format as: DD:HH:MM:SS /proc/uptime give me up time of system in seconds, is there a standard solution that convert seconds to this format?
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0answers
17 views

Why can't I use tab expansion/auto-complete of shell variables with cd?

I have setup a variable in .bashrc: export SOME_DIR=/path/to/some/dir Now, with ls I can type ls $SOME_DIR[tab] and the variable will be expanded, and I can then use tab for auto-completion when ...
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5answers
46 views

How to change to normal user in the command line when logged in as the root user?

I log into an system through root via ssh. How do I become the normal user or another user on the system?
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2answers
5k views

How to check if pipe is empty

I have piped line in bash script and want to check if pipe has data, before feeding program Searching I found about test -t 0 but it doesn't work here. Always returns false. So how to be sure that ...
0
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1answer
20 views

How do I switch from bash to zsh? [duplicate]

I can start zsh with zsh. How can I make it be the default for new terminal windows? Will it be ok to copy my .bashrc to .zshrc to get things like my customized PS1 prompt.
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2answers
51 views

How to find md5sum of files on remote machines by doing ssh?

I am running my below shell script on machineC which gets the md5sum of my files in my PRIMARY directory in machineC itself. #!/bin/bash export PRIMARY=/data01/primary for entry in "$PRIMARY"/* do ...
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1answer
22 views

Permission denied while getting the md5sum of a file using shell script?

I am running my below shell script which gets the md5sum of a files in my PRIMARY directory #!/bin/bash export PRIMARY=/data01/primary for entry in "$PRIMARY"/* do local_md5sum=/usr/bin/md5sum ...
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2answers
8 views

How can I sudo su and change directory just after?

I would like to create an alias that does something like this: alias userYYY='sudo su userYYY; cd /a/path/that/only/userYYY/has/access' So then from my command line, I am logged in with a sudoer ...
1
vote
1answer
8 views

Increase character width in Ubuntu server shell?

Is there any way to increase the character width from 80 to something higher in the shell in an Ubuntu server?
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2answers
223 views

Is there any CLI/terminal slideshow app?

I'm asking myself: is there, on linux, any software that can build and show simple slides on terminal, like the slides you make on Libreoffice Impress (but way more simple)? This would be a great ...
3
votes
1answer
21 views

More shell scripts than one in one text file?

I am learning shell scripting for my introductory UNIX course at my university, and I`m curious if is it possible to have more than one shell script in one text file. What I mean by that is, for ...
0
votes
1answer
33 views

How to invoke shell function in string? (bash)

I want to invoke shell function in string. Here is my use case: function envfoo() { env ENV_FOO=foo $@ } function envbar() { env ENV_BAR=bar $@ } $ envfoo env |egrep ENV_ ENV_FOO=foo $ ...
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votes
2answers
21 views

Add space after 8 characters then add space after every 4 characters

Here is the sample input: AbbigailAbieAbbyAbbi Using sed, I have separated them into 4 characters but seems like I got a problem because I have to separate the first 8 characters first then add ...
8
votes
4answers
407 views

How do I remove spaces from shell variables?

I have done the following at command line: $ text="name with space" $ echo $text name with space I am trying to use tr -d ' ' to remove the spaces and have a result of: namewithspace I've tried ...
1
vote
2answers
140 views

I accidentally GZIPed a whole bunch of files, one by one, instead of using tar(1). How can I undo this mess?

I'm new to the gzip command, so I googled some commands to run so I can gzip an entire directory recursively. Now while it did that, it converted each of my files to the gzip format and added .gz to ...
5
votes
3answers
90 views

Bash script error with strings with paths that have spaces and wildcards

I am having trouble getting the basics of Bash scripting down. Here's what I have so far: #!/bin/bash FILES="/home/john/my directory/*.txt" for f in "${FILES}" do echo "${f}" done All I want to ...
5
votes
3answers
118 views

I am trying to find a better/easier way to count alphabetic characters in a file or shell variable

I have a file containing the following text: we are going to write something 1 2 3 wc tells me I have 1 line 9 words and 38 characters. I'm looking to count the 26 letters only (a-z, no numbers or ...
19
votes
7answers
30k views

How can I run a cron command with existing environmental variables?

How can I run a cron command with existing environmental variables? If I am at a shell prompt I can type echo $ORACLE_HOME and get a path. This is one of my environmental variables that gets set in ...
2
votes
2answers
700 views

Using sudoers to allow php to run command

I am trying to get my php page to run this command: shell_exec("sudo /home/xbian/433Utils/RPi_utils/codesend {$num}"); So I added this entry to my sudoers file with visudo: www-data ALL=NOPASSWD: ...
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3answers
127 views

bash find using variable

I have an issue I don't understand. It is simple and it should work, but it doesn't. =EDITED exactly what I can see from terminal= I have a list of filenames: [molni@archlinux picasa_album]$ cat LIST ...
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2answers
36 views

Pass arguments to a command run by another user

I have a bash script that is supposed to take some arguments and then run in a different user: test.sh #!/bin/bash sudo su user2 <<'EOF' echo $1 EOF However it prints blank: $ ./test.sh ...
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votes
5answers
3k views

script to scan ip range and return results in a certain format

This script scans IP's and returns a status of Up or Down. How can I alter it so it doesn't scan everything twice? As it sits it scans everything and returns the "Up" addresses only and then scans all ...
2
votes
4answers
3k views

How to copy or move files without being asked to overwrite?

What I've tried: root@host [/home1]# cp -f hello /home3 cp: omitting directory `hello' root@host [/home1]# cp -rf hello /home3 cp: overwrite `/home3/hello/.buildpath'? y cp: overwrite ...
3
votes
2answers
73 views

Extract csv files from path to multiple files in bash

I have a files multiple file path for backup purpose ,now i want to filter it based on ".csv " fromat. I have tried this. filesall=(/home/abc/allfiles/*) files=$((${filesall[@]}|grep -F ".csv")) ...
4
votes
2answers
1k views

changing current working dir with a script

I've read this question and answer, but it doesn't quit fit my problem, even tho it's similar. I'm writing a script (called cpj) that will launch one of my current projects. I have about 5 of them. ...
2
votes
1answer
35 views

how to execute a shell built-in if find found certain files

In general, if we want to execute a command if find identifies files corresponding to certain specs, we can use -exec. But in my case I want to exit the shell/script if find found a match and -exec ...
1
vote
1answer
495 views

Can I use pmap to find out Memory utilization?

I want to measure memory utilization of my Apache Server. Can I use the pmap command and pass all the process IDs of httpd and take that as total utilization? pmap PID1 PID2 .... It seems that pmap ...
2
votes
1answer
73 views

“No such file” warning on terminal launch

I ran a source command on a file that was missing. I forgot about it but later noticed that every time I opened a new terminal, the first line would be a warning about the missing file bash: ...
3
votes
4answers
37 views

How can I get the first match from wildcard expansion?

Shells like Bash and Zsh expand wildcard into arguments, as many arguments as match the pattern: $ echo *.txt 1.txt 2.txt 3.txt But what if I only want the first match to be returned, not all the ...
4
votes
3answers
123 views

Get PID of any command in backgrounded piped sequence of commands

If, in bash, I execute: cmd1 | cmd2 | ... | cmdi | ... | cmdn & where the cmd{1..n} may not be distinct, how do I get the PID of cmdi? Alternatively, how can I signal the cmdi process? (For ...
7
votes
4answers
237 views

Can I specify a redirected input before a compound command?

Bash lets you specify a redirected input before a command: $ <lines sed 's/^/line: /g' line: foo line: bar Bash also lets you redirect input to a compound command like a while loop: $ while ...
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0answers
48 views

what is hexa dump and how to handle in unix? [on hold]

I am trying to extract some portion of text from the file by using awk command, The file is separated by comma. awk -F, '{print $1 FS $3 FS $6}' sample.csv But always I am getting wrong output , ...
2
votes
2answers
45 views

Reference a path name in `find` output results

What I would like to do is to be able to reference a find path name result as a parameter to another command without laboriously typing the full path name. Example: $ find -name testfile path1 ...
0
votes
0answers
28 views

How to get diff for HTML reports?

echo "New defects" echo "===============================" n=0 def_num=0 while read line; do n=$((++n)) if echo $line | grep '^[[:space:]]*>' &>/dev/null; then if [ $(($n % ...
6
votes
2answers
258 views

Compare two files and print matches

Is there anyway to get this through Unix shell scripting? I have a fileA with one column (1000 rows), and fileB with 26 columns(13000 rows). I need to search each value of fileA with fileB and return ...
8
votes
3answers
897 views

How do I take a list and remove it from a file?

I have a long list of domain names that I need to remove from /etc/remotedomains. They're probably not in any particular order in the file. Each domain is on one line. How could I iterate through the ...
1
vote
3answers
34 views

shell script to run on boot on Mac OS X does not run all commands

On OS X, I am trying to use lingon to run a shell script upon booting. I have a file ~/desktop/_admin/boot/bootdocker.sh: #!/bin/bash boot2docker up export DOCKER_HOST=tcp://192.177.59.103:2475 My ...
3
votes
2answers
2k views

Solving “mv: Argument list too long”?

I have a folder with more than a million files that needs sorting, but I cant really do anything because mv outputs this message all the time -bash: /bin/mv: Argument list too long I'm using this ...
27
votes
4answers
1k views

Does /usr/sbin/nologin as a login shell serve a security purpose?

In my /etc/passwd file, I can see that the www-data user used by Apache, as well as all sorts of system users, have either /usr/sbin/nologin or /bin/false as their login shell. For example, here is a ...
7
votes
1answer
284 views

Is it possible to use `find -exec sh -c` safely?

I'm trying to use find to echo 0 into some files, but apparently this only works with sh -c: find /proc/sys/net/ipv6 -name accept_ra -exec sh -c 'echo 0 > {}' \; But using sh -c with find -exec ...
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votes
1answer
41 views

Questions about UNIX [closed]

Which of the following UNIX command is used to find all of the files which have been accessed within last 30 days. find . -stime -30 -exec || \; |more find . -atime -30 -exec || \; |more find . ...
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vote
1answer
2k views

sh script will not execute as root (cron)

I have the following script added to cron. If I add touch thisisatest.file to the first line it will create a file named thisisatest.file, but not execute the rest of the code. If I manually type ...
4
votes
2answers
87 views

How can I force bash to deallocate a brace expanded variable without name?

For benchmarking, I ran the command: for i in {1..100000000}; do echo "$i" line >> file done Bash expanded the braces and stored the list 1 2 3 4 5 6 ... 100000000 in memory. I thought ...
3
votes
1answer
61 views

How do I diff the outputs of two commands?

How can I use the diff command to compare 2 commands' outputs? Does something like this exist? diff ($cat /etc/passwd) ($cut -f2/etc/passwd)
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2answers
59 views

Shell script throws a not found error when run from a sh file. But if entered manually the commands work

Im trying to use the following script to generate a sitemap for my website. When I run it as sh thsitemap.sh I get an error like this and creates an empty sitemap.xml file : thsitemap.sh: 22: ...