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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230 views

How to timestamp a transcripted talk?

I'm trying to mark each paragraph of transcripted text with timestamps of when/where it occurs in the audio. mplayer and emacs are getting me close. mplayer, in the terminal, outputs a stream of ...
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3answers
403 views

Returning a portion of a line matching a pattern

I have a file (file_name) which contains exactly one occurrance of the string "Result: " at the start of a line. I want to print all the characters after the string "Result: " in that line until I ...
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7answers
17k views

How to compare to floating point number in a shell script

I want to compare two floating point numbers in a shell script. The following code is not working: #!/bin/bash min=12.45 val=10.35 if (( $val < $min )) ; then min=$val fi echo $min
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3answers
14k views

Confusing use of && and || operators

I was skimming through an /etc/rc.d/init.d/sendmail file (I know this is hardly ever used, but I'm studying for an exam), and I've become a bit confused about the && and the || operators. ...
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4answers
17k views

Why is echo ignoring my quote characters?

The echo command isn't including the complete text that I give it. For example, if I do: $ echo ' echo PARAM=` grep $ARG /var/tmp/setfile | awk '{print $2}' ` ' It outputs: echo PARAM=` ...
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1answer
1k views

find command with -execdir not reading flags?

I am trying to locate all .jpg picture files in my current directory and sub-directories and move them to another directory. I want the source files to overwrite the destination files, but that is ...
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4answers
312 views

Generate lists of page numbers for 2-up duplex printing: 2,3,… and 1,4,…

How can I generate the following increments? 2,3,6,7,10,11,14,15,18,19,22,23,26,27,30,31,34,35,38,39,42,43,46,47,...,135 and ...
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3answers
1k views

cp launched from code results in cannot stat '/tmp/somedir' works in shell

I'm working on making some scripts more elegant by implementing them in a real x application etc... At some point in the scripts we basically want to take everything from a mounted removable storage ...
21
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4answers
14k views

Converting relative path to absolute path

Is there a *nix command to get absolute(and canonicalized) path from relative path(with current path) or symbolic link?
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0answers
274 views

python error using an executable with Z shell

I'm getting this error from the Unix Z shell (I'm on Mac): python: posix_spawn: /System/Library/Frameworks/Python.framework/Versions/2.6/Resources/Python.app/Contents/MacOS/Python: No such file or ...
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7answers
3k views

Bash - Continuous String Manipulation

#!/bin/bash FILE="$(basename "$1")" FILE="${FILE/%.jpeg/.jpg}" Is there anyway to glue these two lines together into a one-liner?
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6answers
2k views

Portable way to find inode number

At first I used stat -c %i file (to help detect the presence of a jail), which seemed to work on any Linux distribution under the sun. On OS X' I had to use ls -i file | cut -d ' ' -f 1. Is there ...
29
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1answer
967 views

Avoiding “BASH-isms” in shell scripts

Does there exist a tool similar to Perl::Critic that will inspect your shell scripts and point out flaws, portability issues, uses of non-standard programs without fallbacks, depreciated program uses, ...
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3answers
3k views

Are two files hardlinked?

How can I tell if two files are hard-linked from the command line? e.g. something link this: $ ls fileA fileB fileC $ is-hardlinked fileA fileB yes $ is-hardlinked fileA fileC no
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6answers
2k views

Remove empty directory trees (removing as many directories as possible but no files)

Suppose I have a dir tree like this: ROOTDIR └--SUBDIR1 └----SUBDIR2 └----SUBDIR3 I am looking for a command such that when I input: $ [unknown command] ROOTDIR The whole ...
2
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0answers
99 views

“cd //” and “cd /” what is the difference? [duplicate]

Possible Duplicate: unix, difference between path starting with '/' and '//' If I make a cd // followed by a pwd I see: # cd // # pwd // why is that? what's the differece ...
5
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5answers
259 views

Is there a way to see the permissions of all the intermediate directories of a path..?

I have a file path.. Is there any single command to see the file/directory permissions of all the intermediate directories in the path..?
2
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3answers
2k views

Returning only the portion of a line after a matching pattern

I have a file (file_name) which contains exactly one occurance of the string Result:, at the start of a line. I want to print all the characters after the string Result: in that line until I encounter ...
1
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3answers
788 views

Writing a shell script to take output of an executable and perform some calculation

I am not much familiar with shell script. I want to write a shell script for the following pseudo-code: min=some garbage value for(i=1 to N){ // N and n will be taken as input for the shell script. ...
3
votes
4answers
759 views

Find a string (like grep -q) within only a section of a file

I want to write some Bash that can verify that a string exists in a configuration file. I can't change the file format, it belongs to a different application. The file is subdivided into groups named ...
4
votes
3answers
972 views

Delete matching file from every subfolder of current dir

I used this one to copy file in every dir: find -type d -maxdepth 1 -print0 | xargs -0 -n1 cp .htaccess Now i need to do reverse one and delete file with matching name from every sub directory of ...
23
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4answers
14k views

How do I exit a script in a conditional statement?

I'm writing a bash script where I want to exit if the user is not root. The conditional works fine, but the script does not exit. [[ `id -u` == 0 ]] || (echo "Must be root to run script"; exit) ...
2
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1answer
582 views

How to insert a first column to many files + how to convert unix time to normal time

There are many-many files in a directory that has e.x.: the following content: INPUT: root 1324711901 sshd 1272725792 And I'm searching for a solution how to convert the content of the ...
8
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5answers
6k views

Run script in a non interactive shell?

I have a cron job that is running a script. When I run the script via an interactive shell (ssh'ed to bash) it works fine. When the script runs by itself via cron it fails. My guess is that it is ...
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1answer
71 views

Program to upgrade configuration files

When upgrading Ubuntu (and probably other *nixes), the upgrade process will show a diff of changed configuration files and ask whether I'd like to replace them, keep the old version, or manually merge ...
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2answers
6k views

How to get a clean environment in a ksh shell?

I need to get rid of all the environment variables in a Ksh shell. I can fork a new instance, but it will inevitably source some init files (as far as I know .profile, .kshrc). Is there a way to ...
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3answers
4k views

What are the significant differences between different shells? [duplicate]

Possible Duplicate: What are the fundamental differences between the mainstream *NIX shells? If I write a shell script in bash, will it run in ksh as well? if not, what are the ...
4
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3answers
847 views

What is a subshell (in the context of the documentation of make)?

I'm reading a book about the make command and there is a paragraph: If any of the prerequisites has an associated rule, make attempts to update those first. Next, the target file is considered. ...
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8answers
7k views

Can shell variable include - character?

I am not able to use - in variables in shell. Is there a way to be able to use it, because I have one script which depends on such named variables: $export a-b=c -bash: export: `a-b=c': not a valid ...
2
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3answers
4k views

Bash string replace multiple chars with one

I'm replacing, from a feed title, all chars except letters and digits with a dash to use the result as a safe filename for any filesystem: $ t="Episodie 06: No hope of riding home (NEW) - Advanced ...
5
votes
3answers
610 views

What does the syntax on this shell command with extglob mean?

In Building paths robustly, A solution is proposed that includes: shopt -s extglob; dir="${dir//+(\/)//}" Can someone explain (parse) that for me? I understand what it's doing, but not how the ...
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3answers
1k views

How to stop a bunch of processes on unix fast?

How to stop a bunch of processes on unix fast. I can use ps/top, kill. If the number of processes is very large, I use shell script. Are there other ways, only one or two unix commands can do it ...
9
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1answer
963 views

Why am I getting 'Name collision between …' errors and how can I fix them?

Every time I try to launch vim or emacs or even top (I think it's actually any command that uses ncurses) in a unix terminal (on a cluster computer over ssh), I get a a continuous stream of 'Name ...
5
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1answer
3k views

Wrapping a command that includes single and double quotes for another command

I recently learned about watch, but am having trouble making it work with relatively sophisticated commands. For example, I would like to ask watch to run the following command on zsh every three ...
2
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1answer
269 views

How to keep a line from being remembered in the history?

This is for a single line, not a command. I found the way to make it always prevent history for a single command. Thanks. EDIT: Sorry for the poor wording. Single line - For example, if I type, git ...
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3answers
5k views

How to “send” variable to sub-shell?

I run the following script: VAR="Test" sh -c 'echo "Hello $VAR"' But I get : # ./test.sh Hello How can I "send" the variable VAR of my script to the shell created with sh -c?
2
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2answers
5k views

How to exclude a list of full directory paths in find command on Solaris

(Duplicated from Stack Overflow: http://stackoverflow.com/questions/7854975/how-to-exclude-a-list-of-full-directory-paths-in-find-command-on-solaris) I have a very specific need to find unowned files ...
1
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2answers
1k views

Process list: /bin/sh -e /proc/self/fd/11

I got this: PID TTY STAT TIME COMMAND 2 ? S 0:00 [kthreadd] 3 ? S 0:00 \_ [migration/0] : 844 ? S 0:00 \_ [vmmemctl] 1 ? ...
0
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2answers
983 views

Combination of ls, xargs and zcat leads to duplicate file name suffixes?

Disclaimer: Yes, finding files in a script with ls is bad, but find can't sort by modification date. Using ls and xargs with echo everything is fine: $ ls -t1 ssl-access*.gz | xargs -n 1 echo ...
1
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2answers
166 views

How to log if an environment variable is unset? [closed]

How can I write a shell script that checks for an environment variable and writes to a log file if the variable is unset? Also, if the file name pointed by env variable doesn't exist, how to create ...
5
votes
3answers
347 views

For a same unix or linux user, different sets of environment variables

I'm using tcsh, and for a specific project every member of my team connects to a server with the same user. (This is something we cannot change). The situation arises because I want to have some ...
2
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1answer
2k views

pass 1 environment variable using sudo

Is this a correct way for passing an environment variable in sudo ? sudo -u www-data -b env FOOBAR="foobar" /home/user/folder/daemon
0
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2answers
2k views

Run in root shell from within a user bash script

I have a script that , among other things, needs to do some stuff as root, like creating a mount folder. I tried: echo "Linux user password is needed in order to ..." sudo -s # also tried: # sudo su ...
5
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4answers
2k views

Where do I change my shell?

If I wanted to use zsh, for instance, rather than bash, where would I make this change for the current user?
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6answers
10k views

Shell script for moving oldest files?

How do I write a script for moving just the 20 oldest files from one folder to another? Is there a way to grab the oldest files in a folder?
36
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2answers
2k views

Why is '.' a hard link in Unix?

I've seen many explanations for why the link count for an empty directory in Unix based OSes is 2 instead of 1. They all say that it's because of the '.' directory, which every directory has pointing ...
2
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4answers
921 views

Can I pass files between commands?

I am looking for a way to send the resulting file from one comamnd to another, So I dont have to save a copy on disk inbetween. For example, if I have rared files on disk and want to open them I would ...
27
votes
2answers
1k views

What does a “< <(…)” redirection mean?

I've seen that rvm (ruby version manager) is installed using the following command: bash < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer ) So as I ...
2
votes
2answers
6k views

extract middle section of lines of a text file?

I am writing a php script to parse a large text file do to database inserts from it. However on my host, the file is too large, and I hit the memory limit for php. The file has about 16,000 lines; I ...
1
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1answer
311 views

Check a bash variable against a file

I have a bash variable ($HTTP_COOKIE) which contains a string. I want to check if this string matches the content of a given file (token). I'm working on a busybox linux. How should I do?