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Questions tagged [options]

Passing options like -l or --word to commands, or parsing them in scripts

327
votes
10answers
133k 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 ...
108
votes
3answers
189k 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 ...
58
votes
1answer
3k views

What is the actual purpose of GNU grep's -X option and why is it undocumented?

By reading this question, I have discovered that GNU grep has a -X option which expects an argument. Strangely, it is mentioned neither in the man page nor in the info page. Looking at the source ...
49
votes
6answers
21k 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 ...
48
votes
7answers
10k 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, other ...
45
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 - ...
40
votes
2answers
74k 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 ...
33
votes
4answers
7k 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 ...
30
votes
5answers
34k 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 ...
26
votes
2answers
23k views

What is the difference between “du -sh *” and “du -sh ./*”?

What's the difference between du -sh * and du -sh ./* ? Note: What interests me is the * and ./* parts.
26
votes
2answers
2k 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 ...
24
votes
6answers
1k 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 ...
24
votes
3answers
35k 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 ...
23
votes
2answers
2k 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' * ...
21
votes
3answers
3k views

The precedence of command options?

I know that rm -f file1 will forcefully remove file1 without prompting me. I also know that rm -i file1 will first prompt me before removing file1 Now if you execute rm -if file1, this will also ...
20
votes
1answer
1k views

Why does -a in “#!/bin/sh -a” affect sed and “set -a” doesn't?

If I run the following .sh file: #!/bin/sh -a echo "a" | sed -e 's/[\d001-\d008]//g' The result is an error: sed: -e expression #1, char 18: Invalid range end But if I run the following .sh file:...
18
votes
6answers
13k 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?
17
votes
3answers
2k views

Why do options in a quoted variable fail, but work when unquoted?

I read about that I should quote variables in bash, e.g. "$foo" instead of $foo. However, while writing a script, I found an a case where it works without quotes but not with them: wget_options='--...
17
votes
4answers
54k 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';; ...
16
votes
4answers
811 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 ...
15
votes
4answers
33k 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 ...
15
votes
2answers
3k views

Why can spaces between options and parameters be omitted?

For example: xargs -n 1 is the same as xargs -n1 But if you look at the man page, the option is listed as -n max-args, which means the space is supposed to be preserved. There is nothing about ...
15
votes
2answers
25k 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. ...
13
votes
2answers
21k views

What's the difference between a flag, an option, and an argument? [closed]

ls -a (I consider -a an option) sudo -u username (-u = option, username = arg) chmod 664 my-dir (664 = option, my-dir = arg) I can't think of an example that might say "this is a flag" except perhaps ...
12
votes
1answer
14k views

Do you need to specify the “defaults” option in fstab?

The Arch Wiki on fstab specifies the options of / to be defaults,noatime, but on my installation the default fstab is created with the options of rw,relatime. The Arch Wiki covers the atime issues. ...
11
votes
3answers
22k 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 ...
10
votes
3answers
3k 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 ...
10
votes
1answer
10k 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 "--no-color\n--format-doc\n--no-...
9
votes
2answers
11k 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?
9
votes
3answers
10k views

Negative arguments to head / tail

Variants of this question have certainly been asked several times in different places, but I am trying to remove the last M lines from a file without luck. The second most voted answer in this ...
8
votes
1answer
6k views

Finding a file starting with '-' dash [duplicate]

I have the following situation: $ ls 0.txt aaa.txt a-.txt a.txt b.txt ddd.txt -hello.txt libs -.txt ,.txt !.txt ].txt \.txt $ ls [-a]*.txt ls: opzione non valida -- "e" Try 'ls --help' ...
8
votes
2answers
7k 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 ...
7
votes
2answers
4k views

What does ls -alh mean? [duplicate]

I have seen that people use ls -alh in the Linux terminal. However, when I see the manual, I don't see -alh (i.e. when I type man ls). Why do I not have it in the manual? Can someone explain what it ...
7
votes
3answers
2k views

Why does the specific sequence of options matter for tar command?

I was trying out tar command to make archive with .tar extension. please have a look at the following series of commands I tried: $ ls abc.jpg hello.jpg xjf.jpg $ tar -cfv test.tar *.jpg tar: test....
7
votes
1answer
23k 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 "...
7
votes
3answers
9k 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?
7
votes
2answers
3k views

Why does `du -sh *` complain about invalid options?

I've searched my best through Google, but for the life of me I can't figure out what to use instead of * (asterisk) after a recent update (even Wikipedia seems to think du -sh * and du -sh * should ...
7
votes
3answers
7k 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' ...
6
votes
3answers
6k views

diff --git unknown option

when I try to run diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c I get unknown option (I have installed git via apt-get install git)
6
votes
3answers
9k views

What does the option -9 mean for killall?

I saw the command killall -9 but there is not such a option in the man page. So now I'm a bit confused: what does -9 option mean?
6
votes
1answer
239 views

How can I delete a file named “--append”? [duplicate]

By mistake I have created a file named : --append. How do I delete it? Simply entering the usual command, rm -f --append, doesn't work.
6
votes
2answers
3k views

grep the man page of a command for hyphenated options

When I grep the man page of the find command for matches to type it returns a lot of search results that I don't want. Instead I want to use a command that returns only the search results for -type. ...
6
votes
1answer
2k 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 ...
6
votes
3answers
940 views

Set awk array on command line?

I know the -v switch can be used to awk on the command line to set the value for a variable. Is there any way to set values for awk associative array elements on the command line? Something like: ...
6
votes
2answers
22k views

The -cp option to the java command [closed]

java -cp FILE.jar FILE.Main inputfile What does the -cp option mean? For that matter, what a negative sign in front mean? I've searched everywhere and couldn't find the answer.
6
votes
3answers
12k views

Optional arguments after or before the mandatory arguments?

I'm creating a shell script and I need it to take two mandatory arguments and one optional. How do I check that? In most scripts I've seen, the optional arguments are passed before the mandatory ones, ...
5
votes
4answers
638 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
3answers
252 views

Portable way to invoke tar with a list of files from stdin

I want to create a .tgz from the content of a directory. I also want to strip the leading "./" from the tar'ed content. I had done this as follows: cd /path/to/files/ && find . -type f | cut -...
5
votes
2answers
682 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
1answer
605 views

How to distinguish between a positional parameter and an option?

Both a positional parameter ($1, $2, and so forth) and an option (and/or argument) are both written directly after a command, so what is the definition or phrasing to explain how to distinct them? In ...