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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 ...
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 ...
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.
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 ...
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 "...
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 ...
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 ...
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 ...
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 - ...
5
votes
1answer
1k views

Mapping metadata with avconv does not work

The way I understand man avconv (version 9.16-6:9.16-0ubuntu0.14.04.1), the following command should convert input.ogg to output.mp3 and carry over metadata: avconv -i input.ogg -map_metadata 0 ...
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 ...
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' * ...
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 ...
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' ...
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. ...
2
votes
1answer
594 views

Simpler processing of shell script options

I'm looking for way to process shell script arguments that is cleaner and more "self documenting" than getopt/getopts. It would need to provide... Full support of long options with or without a ...
2
votes
2answers
2k views

Parsing of command line options

For I school project, I have to implement a shell/terminal app. But I am wondering how are command line options parsed, because it appears abit weird to be. For example for the command paste (and I ...
3
votes
4answers
3k views

Parsing process command-line arguments from pargs in a shell script

I get list of PIDs in my bash scripts (Java processes) and have to analyze their command-line arguments to determine which instance of server each PID corresponds to. At the moment I do it that way ...
2
votes
1answer
455 views

Using apropos command with -a to search multiple keywords on CentOS 7

I'm running CentOS 7.0 build 1503. I'm trying to search for commands I don't know the name of by searching the man descriptions for multiple keywords using AND (e.g. search for a command containing ...
0
votes
1answer
577 views

What's the -alhF flag in ls?

What is the -alhF flag in ls? I can't find it in the man page.
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 ...
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 ...
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 ...
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 ...
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 ...
5
votes
1answer
132 views

Why did “argument can be squished against option” prevail over “argument is always separate”?

Inspired by the recent question Why does the specific sequence of options matter for tar command?, in which the asker learned why tar -cfv test.tar *.jpg doesn't work, I'd like to ask a followup: ...
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' ...
5
votes
3answers
4k 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
1answer
121 views

Abbreviated long options on the command line of xclip

In the manpage of xclip -selection specify which X selection to use, options are "primary" to use XA_PRIMARY (default), "secondary" for XA_SECONDARY or "clipboard" for XA_CLIPBOARD Note that ...
3
votes
2answers
2k views

The discrimination between short and long option is only `-`?

On Unix system, options begin with - is short option, while options begin with -- is long option. Is my understanding right?
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....
5
votes
2answers
108 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 want ...
3
votes
4answers
2k views

grep getting confused by filenames with dashes

I'm having a problem where grep gets confused when the directory contains a file starting with dashes. For example, I have a file named "------.js" . When I do something like grep somestring * I get ...
3
votes
3answers
474 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 ...
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
3answers
941 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: ...
5
votes
1answer
273 views

Why do some utilities parse operands before options?

According to several sources, the UNIX utility guidelines specify that operands should always be processed after options: utility_name[OPTIONS][operands...] Some older UNIX utilities are known to ...
5
votes
1answer
3k 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 levels][--help][--...
4
votes
1answer
463 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, ...
3
votes
1answer
514 views

Meaning of the double dash in options [closed]

I've read that all multi-character command options must be preceded by a double dash (--). But many flags for the find command (e.g. -name or -type) are preceded by only one dash. Why is that?
3
votes
3answers
386 views

How to read this tcpdump man page?

I am trying to use the tcpdump command in a project and I have some difficulties understanding the help page. SYNOPSIS tcpdump [ -AbdDefhgHIJKlLnNoOpPqRStuUvxX ] [ -B buffer_size ] [ -c count ] ...
2
votes
1answer
1k views

What is the `less` command line option to page to the next file at the end of the current one?

I'm sure there used to be an option in less which allowed you to page onto the next file after you reached the end of the current file, so you could just keep *space*ing through a bunch of short files ...
2
votes
1answer
2k views

What is overriding the fstab permissions mounting option?

fstab: LABEL="Shared" /home/howard/Shared/ ntfs permissions,rw,nosuid,nodev,relatime,uid=howard,gid=howard,allow_other,noatime,fmask=033,dmask=022 0 2 Mount with: mount LABEL="Shared" mount ...
1
vote
1answer
1k views

What is the canonical way to implement order independent options in bash scripts? [duplicate]

Possible Duplicate: How do I handle switches in a shell script? Most common shell commands allow the user to specify options in any random order. Positional Parameters like $1 as commonly used in ...
-5
votes
2answers
186 views

Signal the end of option arguments: double dashes `--` vs single dash `-`? [duplicate]

I notice in https://unix.stackexchange.com/a/459007/674, that single dash - is used to signal the end of option arguments. Is it correct that double dashes -- can also signal the end of option ...