Re: [DNG] bash / quote weirdness
Benjamin Riefenstahl said on Fri, 14 Jan 2022 10:33:29 +0100 >Hi Steve, > >> Benjamin Riefenstahl said on Thu, 13 Jan 2022 18:19:23 +0100 >>>Different code paths within Bash. [...] > >Steve Litt writes: >> This is true, but not the explanation for this particular behavior, >> as follows: >> >> [slitt@mydesk ~]$ /usr/bin/cat -n /etc/fstab | cut -b 1-20 | head -n5 >> 1 UUID=730eaf92 >> 2 UUID=41abb5fd >> 3 UUID=96cfdfb3 >> 4 UUID=6F66-BF7 >> 5 tmpfs /tmp tm >> [slitt@mydesk ~]$ "/usr/bin/cat -n" /etc/fstab | cut -b 1-20 | head >> -n5 bash: /usr/bin/cat -n: No such file or directory >> [slitt@mydesk ~]$ "/usr/bin/cat -n /etc/fstab" | cut -b 1-20 | head >> -n5 bash: /usr/bin/cat -n /etc/fstab: No such file or directory >> [slitt@mydesk ~]$ > >I'm sorry, but I don't see it? Can you point out what is suprising to >you here? Both commands contain "/", and both give the same error >message. > >so long, benny I thought you were saying that the cause of "cat -n" /etc/fstab being seen as one command was due to cat not having a full path, so I put a full path in front of it. If you weren't saying lack of a full path is the cause of "cat -n" being considered a single command, then my prepending the full path produces no surprise at all. SteveT Steve Litt Spring 2021 featured book: Troubleshooting Techniques of the Successful Technologist http://www.troubleshooters.com/techniques ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] bash / quote weirdness
Hi, Steve Litt writes: > Benjamin Riefenstahl said on Thu, 13 Jan 2022 18:19:23 +0100 > >>Hi Steve, >> >>Steve Litt writes: >>> [slitt@mydesk ~]$ "cat -n" /etc/fstab | cut -b 1-20 | head -n5 >>> bash: cat -n: command not found >>> [slitt@mydesk ~]$ "cat -n /etc/fstab" | cut -b 1-20 | head -n5 >>> bash: cat -n /etc/fstab: No such file or directory >>> [slitt@mydesk ~]$ >> >>Different code paths within Bash. When there is a "/" in the command >>name, that is a file that has to exist by that exact name (the file >>name can be relative, though). When there is no "/", then and only >>then the command is searched along $PATH, and if it is not found >>there, the error message is different from the other case. > > This is true, but not the explanation for this particular behavior, as > follows: > > [slitt@mydesk ~]$ /usr/bin/cat -n /etc/fstab | cut -b 1-20 | head -n5 Here your shell look for a file called "cat" i /usr/bin. > 1UUID=730eaf92 > 2UUID=41abb5fd > 3UUID=96cfdfb3 > 4UUID=6F66-BF7 > 5tmpfs /tmp tm > [slitt@mydesk ~]$ "/usr/bin/cat -n" /etc/fstab | cut -b 1-20 | head -n5 Here your shell looks for a file called "cat -n" in /usr/bin. > bash: /usr/bin/cat -n: No such file or directory > [slitt@mydesk ~]$ "/usr/bin/cat -n /etc/fstab" | cut -b 1-20 | head -n5 Here your shell looks for a file called "fstab" in a directory called "etc" in a directory called "cat -n " in /usr/bin. > bash: /usr/bin/cat -n /etc/fstab: No such file or directory Given that, I believe Benjamini's explanation still holds. Hope this helps, -- Olaf MeeuwissenFSF Associate Member since 2004-01-27 GnuPG key: F84A2DD9/B3C0 2F47 EA19 64F4 9F13 F43E B8A4 A88A F84A 2DD9 Support Free Softwarehttps://my.fsf.org/donate Join the Free Software Foundation https://my.fsf.org/join ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] bash / quote weirdness
Hi Steve, > Benjamin Riefenstahl said on Thu, 13 Jan 2022 18:19:23 +0100 >>Different code paths within Bash. [...] Steve Litt writes: > This is true, but not the explanation for this particular behavior, as > follows: > > [slitt@mydesk ~]$ /usr/bin/cat -n /etc/fstab | cut -b 1-20 | head -n5 > 1UUID=730eaf92 > 2UUID=41abb5fd > 3UUID=96cfdfb3 > 4UUID=6F66-BF7 > 5tmpfs /tmp tm > [slitt@mydesk ~]$ "/usr/bin/cat -n" /etc/fstab | cut -b 1-20 | head -n5 > bash: /usr/bin/cat -n: No such file or directory > [slitt@mydesk ~]$ "/usr/bin/cat -n /etc/fstab" | cut -b 1-20 | head -n5 > bash: /usr/bin/cat -n /etc/fstab: No such file or directory > [slitt@mydesk ~]$ I'm sorry, but I don't see it? Can you point out what is suprising to you here? Both commands contain "/", and both give the same error message. so long, benny ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] bash / quote weirdness
Hendrik Boom said on Thu, 13 Jan 2022 18:15:28 -0500 >On Thu, Jan 13, 2022 at 12:45:09PM -0500, . via Dng wrote: > >> >> The shell receives a series of tokens, and tries to interpret the >> first one as a command. In the double-quoted attempt above, it gets >> two tokens before the first pipe | --- >> >> 1) "cat -n" >> >> 2) /etc/fstab >> >> Of course, the system has no command named "cat -n". (And only a >> chaotic evil person would use a space in a command's name.) >> Something like "cat" "-n" /etc/fstab > >Maybe to keep anyone from executing a potentially danterous command by >mistake? Yeah, that too. SteveT Steve Litt Spring 2021 featured book: Troubleshooting Techniques of the Successful Technologist http://www.troubleshooters.com/techniques ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] bash / quote weirdness
. via Dng said on Thu, 13 Jan 2022 12:45:09 -0500 >The shell receives a series of tokens, and tries to interpret the >first one as a command. In the double-quoted attempt above, it gets >two tokens before the first pipe | --- > > 1) "cat -n" > > 2) /etc/fstab > >Of course, the system has no command named "cat -n". (And only a >chaotic evil person would use a space in a command's name.) Something >like > "cat" "-n" /etc/fstab > >would work fine, the shell now sees three tokens (and the double >quotes are completely unnecessary here), and the first is recognized >as a command that's on the executable path. > >The same goes for "cat /etc/fstab" or "cat fstab", they're both just >text strings that happen to include a space character. ^^ dng is correct! SteveT Steve Litt Spring 2021 featured book: Troubleshooting Techniques of the Successful Technologist http://www.troubleshooters.com/techniques ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] bash / quote weirdness
Benjamin Riefenstahl said on Thu, 13 Jan 2022 18:19:23 +0100 >Hi Steve, > >Steve Litt writes: >> [slitt@mydesk ~]$ "cat -n" /etc/fstab | cut -b 1-20 | head -n5 >> bash: cat -n: command not found >> [slitt@mydesk ~]$ "cat -n /etc/fstab" | cut -b 1-20 | head -n5 >> bash: cat -n /etc/fstab: No such file or directory >> [slitt@mydesk ~]$ > >Different code paths within Bash. When there is a "/" in the command >name, that is a file that has to exist by that exact name (the file >name can be relative, though). When there is no "/", then and only >then the command is searched along $PATH, and if it is not found >there, the error message is different from the other case. This is true, but not the explanation for this particular behavior, as follows: [slitt@mydesk ~]$ /usr/bin/cat -n /etc/fstab | cut -b 1-20 | head -n5 1 UUID=730eaf92 2 UUID=41abb5fd 3 UUID=96cfdfb3 4 UUID=6F66-BF7 5 tmpfs /tmp tm [slitt@mydesk ~]$ "/usr/bin/cat -n" /etc/fstab | cut -b 1-20 | head -n5 bash: /usr/bin/cat -n: No such file or directory [slitt@mydesk ~]$ "/usr/bin/cat -n /etc/fstab" | cut -b 1-20 | head -n5 bash: /usr/bin/cat -n /etc/fstab: No such file or directory [slitt@mydesk ~]$ SteveT Steve Litt Spring 2021 featured book: Troubleshooting Techniques of the Successful Technologist http://www.troubleshooters.com/techniques ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] bash / quote weirdness
On Friday 14 January 2022 at 00:15:28, Hendrik Boom wrote: > On Thu, Jan 13, 2022 at 12:45:09PM -0500, . via Dng wrote: > > The shell receives a series of tokens, and tries to interpret the first > > one as a command. In the double-quoted attempt above, it gets two > > tokens before the first pipe | --- > > > > 1) "cat -n" > > > > 2) /etc/fstab > > > > Of course, the system has no command named "cat -n". (And only a chaotic > > evil person would use a space in a command's name.) Something like > > "cat" "-n" /etc/fstab > > Maybe to keep anyone from executing a potentially dangerous command by > mistake? That doesn't sound like the standard *nix approach to me. Antony. -- "There is no reason for any individual to have a computer in their home." - Ken Olsen, President of Digital Equipment Corporation (DEC, later consumed by Compaq, later merged with HP) Please reply to the list; please *don't* CC me. ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] bash / quote weirdness
On Thu, Jan 13, 2022 at 12:45:09PM -0500, . via Dng wrote: > > The shell receives a series of tokens, and tries to interpret the first one > as a command. In the double-quoted attempt above, it gets two tokens before > the first pipe | --- > > 1) "cat -n" > > 2) /etc/fstab > > Of course, the system has no command named "cat -n". (And only a chaotic > evil person would use a space in a command's name.) Something like > "cat" "-n" /etc/fstab Maybe to keep anyone from executing a potentially danterous command by mistake? -- hendrik > would work fine, the shell now sees three tokens (and the double quotes are > completely unnecessary here), and the first is recognized as a command > that's on the executable path. > > The same goes for "cat /etc/fstab" or "cat fstab", they're both just text > strings that happen to include a space character. > > > ___ > Dng mailing list > Dng@lists.dyne.org > https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] bash / quote weirdness
On Wed, 2022-01-12 at 00:08 +0100, Florian Zieboll via Dng wrote: Dear list, this im my 'test.sh': #!/bin/bash for f in "$@" ; do xcmd="unrar x" $xcmd "$f" done Can please somebody explain, why, if I double-quote the "$xcmd" variable in line 4, the script fails with ./test.sh: line 4: unrar x: command not found ??? Commands without parameters resp. whitespace (e.g. xcmd="unzip") work fine when double-quoted; a web search (including the "GNU Bash manual" [1]) did not shed any light on this mystery... Thank you and libre Grüße, Florian -- Message: 2 Date: Thu, 13 Jan 2022 09:07:22 -0500 From: Hendrik Boom To: dng@lists.dyne.org Subject: Re: [DNG] [OT] bash / quote weirdness Message-ID: <20220113140722.ga30...@topoi.pooq.com> Content-Type: text/plain; charset=us-ascii On Wed, Jan 12, 2022 at 05:45:08PM -0500, Steve Litt wrote: On the other hand... === [slitt@mydesk ~]$ cat -n /etc/fstab | cut -b 1-20 | head -n5 1 UUID=730eaf92 2 UUID=41abb5fd 3 UUID=96cfdfb3 4 UUID=6F66-BF7 5 tmpfs /tmp tm [slitt@mydesk ~]$ "cat -n" /etc/fstab | cut -b 1-20 | head -n5 bash: cat -n: command not found [slitt@mydesk ~]$ "cat -n /etc/fstab" | cut -b 1-20 | head -n5 bash: cat -n /etc/fstab: No such file or directory [slitt@mydesk ~]$ So if it has parameters it's a command, and if it diesn't it's just a file or directory? -- hendrik -- Message: 3 Date: Thu, 13 Jan 2022 15:43:29 +0100 From: Antony Stone To: dng@lists.dyne.org Subject: Re: [DNG] [OT] bash / quote weirdness Message-ID: <202201131543.29980.antony.st...@devuan.open.source.it> Content-Type: Text/Plain; charset="utf-8" On Thursday 13 January 2022 at 15:07:22, Hendrik Boom wrote: On Wed, Jan 12, 2022 at 05:45:08PM -0500, Steve Litt wrote: [slitt@mydesk ~]$ cat -n /etc/fstab | cut -b 1-20 | head -n5 1 UUID=730eaf92 2 UUID=41abb5fd 3 UUID=96cfdfb3 4 UUID=6F66-BF7 5 tmpfs /tmp tm [slitt@mydesk ~]$ "cat -n" /etc/fstab | cut -b 1-20 | head -n5 bash: cat -n: command not found [slitt@mydesk ~]$ "cat -n /etc/fstab" | cut -b 1-20 | head -n5 bash: cat -n /etc/fstab: No such file or directory So if it has parameters it's a command, and if it diesn't it's just a file or directory? It looks a good deal more complicated than that... $ "cat /etc/fstab" bash: cat /etc/fstab: No such file or directory $ "cat fstab" bash: cat fstab: command not found I have no idea what's really going on here. Antony. The shell receives a series of tokens, and tries to interpret the first one as a command. In the double-quoted attempt above, it gets two tokens before the first pipe | --- 1) "cat -n" 2) /etc/fstab Of course, the system has no command named "cat -n". (And only a chaotic evil person would use a space in a command's name.) Something like "cat" "-n" /etc/fstab would work fine, the shell now sees three tokens (and the double quotes are completely unnecessary here), and the first is recognized as a command that's on the executable path. The same goes for "cat /etc/fstab" or "cat fstab", they're both just text strings that happen to include a space character. ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] bash / quote weirdness
Hi Steve, Steve Litt writes: > [slitt@mydesk ~]$ "cat -n" /etc/fstab | cut -b 1-20 | head -n5 > bash: cat -n: command not found > [slitt@mydesk ~]$ "cat -n /etc/fstab" | cut -b 1-20 | head -n5 > bash: cat -n /etc/fstab: No such file or directory > [slitt@mydesk ~]$ Different code paths within Bash. When there is a "/" in the command name, that is a file that has to exist by that exact name (the file name can be relative, though). When there is no "/", then and only then the command is searched along $PATH, and if it is not found there, the error message is different from the other case. At least that is my explanation. so long, benny ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
