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Thanks - another new one on me - “file" I guess my work is scribbling away as a unix-user. oblivious to the “system” viewpoint. Best wishes, Rich Smith > On 26 Oct 2023, at 00:42, Simon Waters <simon@xxxxxxxxxxxxxx> wrote: > > On Thursday, 19 October 2023 05:11:46 BST rds_met wrote: >> >> "mytrue.sh": >> #!/bin/sh >> exit 0 > > Also (at least in bash): > > simon@rodney:/tmp$ file mytrue > mytrue: empty > > simon@rodney:/tmp$ ./mytrue && echo true > true > > Is that the same? > >> "myfalse.sh": >> #!/bin/sh >> exit 1 > > :) > > "true" and "false" are usually shell builtin commands to avoid the cost of > spawning a process. > > simon@rodney:/tmp$ type false > false is a shell builtin > simon@rodney:/tmp$ type true > true is a shell builtin > > "/bin/false" is used for certain types of accounts where you don't want that > user to be able to spawn a shell (see /etc/passwd). > > Also we now have "/usr/sbin/nologin" to be the default shell which prints a > nice message before failing, somehow "nologin" is smaller than "false" on my > system (presumably no "--version" and "--help" options). > > simon@rodney:/usr/sbin$ /usr/sbin/nologin > This account is currently not available. > > I vaguely recall Unicos had one of the text manipulation commands (I think > "basename") was implemented using totally over the top shell script using > "expr". Be interesting to see the space/performance trade off one could make by > replacing executables like this. > > These days I have 4261 commands in /usr/bin, heck I have 121 with "llvm" in > the command, and I'm pretty sure I only installed that to try something out > with a different compiler the one time, so no way anyone is learning all of > those. > > I have 77 different commands for manipulating Portable Any Maps, that project > is about the same age as Linux, and despite having used them to automate image > manipulation many years ago I've only used a handful of them in anger. > > > > -- > The Mailing List for the Devon & Cornwall LUG > FAQ: https://www.dcglug.org.uk/faq/ -- The Mailing List for the Devon & Cornwall LUG FAQ: https://www.dcglug.org.uk/faq/