Re: Command not found with builtins and variables
Chet Ramey wrote: > b...@feusi.co wrote: > > The thing I noticed is that when setting a variable and then running the > > command "time", bash reports "command not found". For example, the > > command: > > > > TEST=1 time ls > > > > Results in "bash: time: command not found" That would work if you installed the GNU time package. https://www.gnu.org/software/time/ And it would produce the portable output format in both cases with the time -p option, which is available both in the internal time and the external GNU time command. Otherwise GNU time has its own unique and different default output format. $ TEST=1 time -p sleep 1 real 1.00 user 0.00 sys 0.00 But regardless of the external standalone time program... Order when using the internal time here matters. Since 'time' is special it should always be first. Put any variables to be set on the line before the command by putting it before the command but after the 'time' word. $ time TEST=1 sleep 1 real0m1.003s user0m0.000s sys 0m0.000s > You don't have a command named `time' in a directory in your $PATH. Well... *They* don't have a time program in PATH. But they could have if they installed it. And many people do. :-) > Bash doesn't have a `time' builtin; it has a `time' reserved word. > Preceding `time' with a variable assignment removes its special meaning > and causes it to not be recognized as a reserved word. I might also mention that the bash 'time' needs this special status because it times the entire pipeline. $ time sleep 1 | sleep 2 real0m2.004s user0m0.003s sys 0m0.002s Therefore conversely if someone is using the external time it might give them an unexpected result. Since the external time will not know anything about a pipeline. So this might catch people off guard too. $ TEST=foo time -p sleep 1 | sleep 2 real 1.00 user 0.00 sys 0.00 When used it is best to always put 'time' first on the command line, variables second, and commands after that. Order matters[1]. Bob [1] OT: In English the order also matters and it is always opinion, size, age, shape, color, origin, material, purpose, noun. Using any other order and it sounds really odd! Reference "The Elements Of Eloquence: How To Turn The Perfect English Phrase." by Mark Forsyth. http://www.npr.org/2016/09/08/493157931/bbc-editor-highlights-often-overlooked-english-language-rule
Re: Command not found with builtins and variables
On 10/10/18 7:42 AM, b...@feusi.co wrote: > Hi, > I'm not exactly sure if the following is actually a bug or whether bash > is actually supposed to behave like this. However, I couldn't find any > documentation concerning it so I decided to ask. > > The thing I noticed is that when setting a variable and then running the > command "time", bash reports "command not found". For example, the > command: > > TEST=1 time ls > > Results in "bash: time: command not found" You don't have a command named `time' in a directory in your $PATH. Bash doesn't have a `time' builtin; it has a `time' reserved word. Preceding `time' with a variable assignment removes its special meaning and causes it to not be recognized as a reserved word. -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, UTech, CWRUc...@case.eduhttp://tiswww.cwru.edu/~chet/
Re: Command not found with builtins and variables
On Wed, Oct 10, 2018 at 01:42:50PM +0200, b...@feusi.co wrote: > TEST=1 time ls time is not a builtin. It's a "keyword". It's a piece of the shell's syntax. It has special magical rules that apply to nothing else. If you want to set an environment variable in the temporary execution environment of a command, and time how long that command takes, then you write it like this: time TEST=1 something that is not actually ls because ls does not use \$TEST > TEST=1 cd > > Works without any problems, Completely useless. cd does not use environment variables. Stop OBFUSCATING your questions. Post the ACTUAL QUESTIONS with the ACTUAL INTENT so we can answer them.
Command not found with builtins and variables
Hi, I'm not exactly sure if the following is actually a bug or whether bash is actually supposed to behave like this. However, I couldn't find any documentation concerning it so I decided to ask. The thing I noticed is that when setting a variable and then running the command "time", bash reports "command not found". For example, the command: TEST=1 time ls Results in "bash: time: command not found" At first, I believed that this was inherent to the bash builtins but I discovered that TEST=1 cd Works without any problems, so I am confused as to why bash behaves in this manner. Is there any underlying reason to this behaviour or is this a bug? cheers, project-repo
