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52
votes
8answers
13k views

How do I delete a file whose name begins with “-” (hyphen a.k.a. dash or minus)?

How do you remove a file whose filename begins with a dash (hyphen or minus) -? I'm ssh'd into a remote OSX server and I have this file in my directory: tohru:~ $ ls -l total 8 -rw-r--r-- 1 me ...
35
votes
7answers
3k views

Is `-` used only with cd?

cd - can switch between current dir and previous dir. It seems that I have seen - used as arguments to other commands before, though I don't remember if - means the same as with cd. I found that - ...
31
votes
7answers
4k views

why does ls -d also list files, and where is it documented?

when specifying ls --directory a* it should list only directories starting with a* BUT it lists files AND directories starting with a Questions: where might I find some documentation on this, ...
22
votes
4answers
4k views

Single dashes `-` for single-character options, but double dashes `--` for words?

Where did the convention of using single dashes for letters and doubles dashes for words come from and why is continued to be used? For example if I type in ls --help, you see: -a, --all ...
21
votes
2answers
655 views

What is `--` called?

Recently I got to know of -- that is double-hyphen which is used to tell a command that the option list has ended and what follows should not be considered as a option. So, grep -- 'search_word' * ...
16
votes
2answers
13k views

tar cvf or tar -cvf ?

I have learned to use tar without '-' for options, like tar cvfz dir.tar.gz Directory/ but I recently came accross the slightly different tar -czvf syntax (I think the 'f' must be the last option in ...
13
votes
4answers
693 views

Why does ls accept duplicate switches?

I'm curious - is there a difference between ls -l and ls -lllllllllllllllllllllllllllll? The output appears to be the same and I'm confused on why ls allows duplicate switches. Is this a standard ...
13
votes
6answers
688 views

Is there way to see `man` document only for specified option of a command

If I want to know the meaning of wget -b, I see the manual by man wget, then search the -b option. -b --background Go to background immediately after startup. If no output file is ...
13
votes
1answer
19k views

How can I execute local script on remote machine and include arguments?

I have written a script that runs fine when executed locally: ./sysMole -time Aug 18 18 The arguments "-time", "Aug", "18", and "18" are successfully passed on to the script. Now, this script is ...
12
votes
3answers
3k views

Is there a 'rc' configuration file for grep/egrep? (~/.egreprc?)

I usually do some grep when developing, and there are some extensions that I always don't want to look for (like *.pyc). Is it possible to create a ~/.egreprc or something like that, and put some ...
12
votes
2answers
213 views

Security implications of running perl -ne '…' *

Apparently, running: perl -n -e 'some perl code' * Or find . ... -exec perl -n -e '...' {} + (same with -p instead of -n) Or perl -e 'some code using <>' * often found in one-liners ...
10
votes
6answers
6k views

Compiling GNU/Linux with -O3 optimization

It's said that compiling GNU tools and Linux kernel with -O3 gcc optimization option will produce weird and funky bugs. Is it true? Has anyone tried it or is it just a hoax?
9
votes
4answers
6k views

How do I handle switches in a shell script?

Are there some built-in tools that will recognize -x and --xxxx as switches, and not arguments, or do you have to go through all the input variables, test for dashes, and then parse the arguments ...
8
votes
1answer
467 views

How to append multiple lines to a file with bash, with “--” in front of string

Question very similar to How to append multiple lines to a file with bash but I want to start the file with --, and also append to the file, if possible. printf ...
8
votes
3answers
8k views

getopt, getopts or manual parsing - what to use when I want to support both short and long options?

Currently I'm writing a Bash script which has the following requirements: it should run on a wide variety of Unix/Linux platforms it should support both short and (GNU) long options I know that ...
6
votes
3answers
708 views

What's the purpose of `rm -P`?

I was reading the man page for rm when I came across this option: -P Overwrite regular files before deleting them. Files are overwritten three times, first with the byte pattern 0xff, then ...
5
votes
4answers
507 views

How can I create a empty file whose name begins with a dash? [duplicate]

How can we create a empty file with the unix name -stuff. It means the name start with -. I tried with touch -stuff but it didn't work.
5
votes
2answers
286 views

How do you get fgrep to find the literal “--help”?

fgrep --help | fgrep "--help" returns just the whole fgrep --help, how do I return just the lines that have the literal "--help" in them? The quotes don't do anything, nor does \-\-help.
5
votes
2answers
3k views

Download list of files if they don't already exist

If I have a list of URLs separated by \n, are there any options I can pass to wget to download all the URLs and save them to the current directory, but only if the files don't already exist?
5
votes
3answers
279 views

What's the real point of the -f option on rm?

By reading the GNU coreutils man page for rm, one of the options is -f, which according to the manual, -f, --force ignore nonexistent files and arguments, never prompt Now, I made some ...
5
votes
3answers
2k views

Remove many many many files from a folder

I have a folder with 137795 files in it. I need to delete all of them. When I run rm * I get -bash: /bin/rm: Argument list too long. How do I get past this error?
5
votes
1answer
894 views

In the usage string of my custom shell script, shall I also display --help and --version?

I'm currently developing a shell script, called up, which shows a usage string on the commandline when called with --help. The output looks like this: $ up --help usage: up [-n ...
5
votes
2answers
81 views

Handling an option-like filename in the shell [duplicate]

Possible Duplicate: How do I delete a file whose name begins with "--"? Due to mismatched switches when I was trying to run a command, I have a log file named -w in a directory. I ...
5
votes
1answer
252 views

Handling filenames that contains a hyphen, within a script

I have few files that was incorrectly encoded, during extraction, file names now become something similar to -a -b, Now I'm trying to fix this issue with: convmv -f ENCODING -t utf8 --notest * But ...
5
votes
1answer
191 views

Provide two arguments to one option using getopts

In below code when I give option r then getopts requires one arguments: while getopts ":hr::l:" opt; do case $opt in r ) echo "Run Numbers - argument = $OPTARG " ;; l ) echo ...
5
votes
1answer
61 views

how to input this command line

hume@linux-o1dm:~> gnomesu -u legum java -jar '/home/legum/frem/frem.jar' Unknown option -jar I want -u for gnomesu and -jar for java, but the openSUSE treat -u -jar only for gnomesu. What is ...
5
votes
2answers
55 views

Is it possible for bash completion to cycle through the alternatives?

When using bash completion and an a number of characters have been entered, tabbing ceases to work then the prefix you have typed is matched by more than one of the possibilities. Is there a way to ...
4
votes
3answers
551 views

What is a “non-option argument”?

I am trying to understand info who but completly fail at the term »non-option argument«. Can someone please explain this term to me in simple words or an example? UPDATE: from ' info who' ...
4
votes
2answers
9k views

How can I detect that no options were passed with getopts?

I have this code - #getoptDemo.sh usage() { echo "usage: <command> options:<w|l|h>" } while getopts wlh: option do case $option in (w) name='1';; ...
4
votes
3answers
3k views

convert soft- to hardlinks with cp

The cp command's infopage offers on the option --preserve= the following: links Preserve in the destination files any links between corresponding source files. Note that with -L' ...
4
votes
2answers
2k views

what is commit=0 for ext4? does mdadm not support it?

I see this in my dmesg log EXT4-fs (md1): re-mounted. Opts: commit=0 EXT4-fs (md2): re-mounted. Opts: commit=0 EXT4-fs (md3): re-mounted. Opts: commit=0 I think that means that dealloc is disabled? ...
4
votes
2answers
4k views

syntax of ls --hide= and ls --ignore=

ls --hide and ls --ignore provides the possibility leave out files defined through regular expressions set after the --ignore= part. The latter makes sure that this option isn't turned off via -a, -A. ...
4
votes
1answer
141 views

If I'm logged in as root, how do I restart mysql or apache with options?

I know the commands to restart/stop/start, but when I try to pass options it doesn't seem to work! CENTOS 6, MySQL 5.14 service mysql restart service httpd restart Then I tried this: ...
4
votes
1answer
55 views

POSIX usage standards for requiring at least one optional arg

So, I'm writing a CLI for an API, and I ran into a point where one of the commands support has two optional arguments, id and fields I want to know how to show that these arguments are optional, BUT, ...
4
votes
1answer
2k views

What does Linux's “nointremap” option do?

Ubuntu 12.10 alpha 2 works perfectly on my new 11" 2012 Macbook Air, but only when I boot with the "nointremap" option. Supposedly this is not good to use as a permanent solution. What exactly does ...
3
votes
4answers
234 views

Test if command accepts a specific option

What is the preferred way to test if a command takes an option? What are the caveats? As a motivating example, at login my shell aliases grep to add several --exclude-dir options but this option is ...
3
votes
3answers
205 views

Interactive command usage reference: do you generally have that on Unix?

The question of why some commands rely on manpages whereas others rely on something like the --help flag for providing command usage reference is not new. There is usually a difference in scope ...
3
votes
2answers
702 views

Is it possible to disable verbose in the middle of running?

I am running a program fls (from the Sleuth Kit) with option -v for verbose mode. However it takes too long, and the program is still running since yesterday. I guess it will run faster without ...
3
votes
1answer
269 views

Understanding grep --label=

I am looking for an explanation how grep --label=LABEL works: Maybe somebody can give me an example [or two] on what --label= is for. I understand what grep and zgrep are supposed to do – the ...
3
votes
2answers
4k views

How to catch optioned and non optioned arguments correctly?

I want to write a shell script which will take some arguments with some options and print that arguments. Suppose the name of that script is abc.ksh. Usage of that script is - ./abc.ksh -[a ...
3
votes
2answers
600 views

Passing arguments to su-provided shell

man su says: You can use the -- argument to separate su options from the arguments supplied to the shell. man bash says: -- A -- signals the end of options and disables further option ...
3
votes
1answer
99 views

What is “userdel --root?” supposed to do

On a GNU/Linux system, I found the following, (for me very confusing seeming entry) about an option for userdel in the German version of its man page: I'm truly sorry, but I can't really provide ...
3
votes
1answer
2k views

xmessage over ssh

The following command prints a message over ssh : xmessage Message -display :0 & How does it work? there is no -display option in xmessage's man page.
3
votes
2answers
430 views

Privileged mode in bash

I've used bash for years but I 've stuck with the"privileged mode" that it can be configure with the set command. For example: set -p I've read the bash man page but it's somewhat obscure. For ...
3
votes
2answers
1k views

cp -L vs. cp -H

Problem When copying files with cp -H or cp -L, I get the same results: $ ls -l fileA fileA -> fileB $ cp fileA somewhere/ -H $ ls -l somewhere/ fileA # fileA is a copy of fileB, only ...
3
votes
2answers
736 views

Getopts option processing, Is it possible to add a non hyphenated [FILE]?

I'm using getopts for all of my scripts that require advanced option parsing, and It's worked great with dash. I'm familiar with the standard basic getopts usage, consisting of [-x] and [-x OPTION]. ...
3
votes
1answer
3k views

How to run a specified codeblock with getopts when no options or arguments are supplied?

So I am writing a script that mixes options with arguments with options that don't. From research I have found that getopts is the best way to do this, and so far it has been simple to figure out and ...
3
votes
1answer
49 views

“mke2fs -r fs-revision-level” - how is this used?

mke2fs -r offers Set the filesystem revision for the new filesystem. Note that 1.2 kernels only support revision 0 filesystems. The default is to create revision 1 filesystems. Trying to ...
3
votes
1answer
236 views

mount --no-canonicalize?

Neither man nor info page provide more information on this than: mount --no-canonicalize Don't canonicalize paths. The mount command canonicalizes all paths (from command line or fstab) ...
2
votes
2answers
2k views

List of available command options?

I'm currently setting up my first web server without a control panel and so far things are going pretty good! I was just wondering if anyone could direct me to somewhere that explains all of the ...