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

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41
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 - ...
3
votes
2answers
33 views

Function with many arguments but only one switch

I am effectively making a recycling bin via some scripts I made. The first script is pretty much an alternative to the rm command (instead of actually deleting a file, it moves it to a deleted ...
6
votes
2answers
129 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.
16
votes
2answers
519 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 ...
19
votes
3answers
491 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 ...
1
vote
0answers
16 views

Using rsync with the verbose option and filtering the information displayed

I am using rsync with the -a -r and -v options to copy files and directories from one server to another. This all works fine. But when I make a change, for example, to a single file on the source ...
5
votes
1answer
2k 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 ...
2
votes
2answers
241 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)
2
votes
3answers
58 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 ] ...
5
votes
2answers
3k 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 ...
1
vote
1answer
48 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 ...
75
votes
9answers
25k 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 ...
24
votes
2answers
43k 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 ...
0
votes
1answer
63 views

What's the -alhF flag in ls?

What is the -alhF flag in ls? I can't find it in the man page.
4
votes
2answers
14k 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
1answer
301 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 ...
1
vote
2answers
128 views

How to extract unknown arguments within a shell script?

I have a shell script that accepts a variety of options, some with arguments, some without, some short, some long. It should handle some of these options itself and pass on the rest it does not know ...
10
votes
3answers
12k 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 ...
2
votes
1answer
68 views

Order between options and operands?

When using a utility program, we may specify options (and their option arguments) and/or operands. In most cases (in the sense of conforming to some standard (POSIX?)) does the order between ...
1
vote
0answers
53 views

Why is rm -r the same as rm -R?

If you look in the rm man page you see that rm -r, rm -R, and rm --recursive are all the same. -r, -R, --recursive remove directories and their contents recursively When using options, I'm ...
1
vote
2answers
74 views

how to delete file that start with “-” [duplicate]

I try to delete this file on my solaris machine rm "-Insi" rm: illegal option -- I rm: illegal option -- n rm: illegal option -- s I also try this rm "\-Insi" -Insi: No such file or directory ...
3
votes
1answer
407 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. ...
14
votes
2answers
4k views

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

The title says it all. What's the difference between those 2 commands? NOTE: I'm more interested in the * and ./* part.
2
votes
1answer
24 views

Why did “argument can be squisehd 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: ...
4
votes
3answers
578 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: ...
0
votes
1answer
214 views

What does the option -C achieve in ls output?

In the man pages it says: -C list entries by columns However, I really cannot notice any difference between the output of ls or ls -C, could someone explain this to me?
3
votes
1answer
61 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 ...
20
votes
6answers
856 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 ...
4
votes
1answer
315 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 ...
1
vote
1answer
26 views

How do I specify command invocation for a mandatory short or long option?

I'm writing a specification for a tool that needs a -f / --foo option with a mandatory argument BAR, so for example these are valid calls: tool -f BAR tool --foo BAR How do I specify this syntax in ...
0
votes
2answers
26 views

why some programs needs -h and other no

I know that is not a exciting question, but yet I don't understand why some programs needs program -h and other program --help sometimes is very boring recognize it
2
votes
2answers
42 views

Is there a `--paranoid` type flag for common, potentially irreversible commands?

I'm not aware of any standard flag that is implemented. There are some git commands that let you specify a -n parameter that will show you what the command is going to do, but doesn't actually do it. ...
2
votes
1answer
92 views

Strange leading whitespace in OPTARG when using getopts

I spent quite a while researching the problem I encountered but none of the getopts tutorial say anything about the leading whitespace in OPTARG when using getopts. In bash(on Ubuntu and OSX), ...
1
vote
1answer
188 views

How to know DHCP options value on debian/ubuntu and other linux

How to know all DHCP options and values (on the client side, Linux Ubuntu / Debian / ArchLinux ) provided by the server. I need to pass non-standard option to the client by the DHCP option code ...
2
votes
2answers
499 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, ...
10
votes
4answers
9k 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 ...
0
votes
0answers
22 views

rpm :deptype flags explained

On Fedora 20 (Heisenbug) I issed the following command … rpm --query --queryformat="%{REQUIREFLAGS:deptype}\n" --all | sort --unique --dictionary-order … to get all possible :deptype ...
0
votes
1answer
42 views

Options to a command specified in a file

How can I have some of the options to a unix command come from a file? That is the file does not contain all the options -- other options are specified elsewhere. For example I have the ...
2
votes
2answers
2k views

How to find every symbolic link on a server?

I need to find every symbolic link on the server. The version is AIX 6.1. man find says -L Follow symbolic links But find -L is not a proper usage. Usage: find [-H | -L] Path-list ...
11
votes
6answers
7k 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?
2
votes
1answer
115 views

FAT Mountoption allow_utime explained

I trying to figure out what the following Mountoption for (v)FAT exactly does (in Linux): allow_utime=### -- This option controls the permission check of mtime/atime. 20 - If ...
2
votes
2answers
734 views

How to change a firefox option on a quick way (via shortcuts, command line,..)?

In Firefox we have two options at Firefox->Preferences->Preferences->Fonts and colors->Colors menu, Use system colors and Sites can use other colors. I would like keep the first one ...
3
votes
4answers
348 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 ...
1
vote
1answer
193 views

in which units does tar --checkpoint measure?

GNU tar offers the option --checkpoint where a message should be printed each checkpointreached. Question:: In what does --checkpoint measure? My best guess is Bytes. I wasn't able to find a hint ...
2
votes
1answer
47 views

Understanding passwd --keep-tokens

On GNU/Linux, I do have trouble understanding the meaning of the --keep-tokens option for passwd. As it doesn't seem to be much used as I am not able to find any examples and only online copies of man ...
15
votes
4answers
712 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 ...
5
votes
2answers
357 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.
3
votes
3answers
263 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 ...
2
votes
1answer
52 views

What is a command that will only show me the command syntax and options?

Is there a command which will just list all the options for a given command on one or two lines and not as long and words as man or info ?
8
votes
1answer
1k 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 ...