Antony Stone said on Thu, 13 Jan 2022 15:43:29 +0100
>$ "cat fstab" >bash: cat fstab: command not found > >I have no idea what's really going on here. > > >Antony. Hi Anthony, Different programs handle commands with arguments different ways. sed -e handles the string that follows, which must be in quotes, as several different words. The C system() function handles its one string argument the same way, busting it into words delineated by spaces or beginning or end of line. On the other hand, the C execve() function is fed an array of strings, and doesn't do any splitting itself. Likewise, my /bin/sh, which I believe is a symlink for dash, takes a series of whitespace separated strings. If you quote something with a one or more spaces inside, dash considers the entire quoted entity to be exactly one string. This is one reason why, in shellscripts, you need to quote almost all variables: So they act correctly with the space laden filenames that windows dwoobydogs just love to create. Here at Troubleshooters.Com, spaces and all punctuation except underscore and hyphen are forbidden, but files coming in from the outside have horrible filenames. I'm pretty sure that, pertaining to quotes and whitespace, bash acts like my dash. I quit using bash in shellscripts after that horrific SHELLSHOCK security flaw (CVE-2014-6271) in 2014 and never came back. Dash has a smaller attack surface. This isn't to say I don't use bash. It's a spectacular interactive shell. But I never use it for shellscripts. In 2014 I had to rewrite over 100 shellscripts to use #!/bin/sh instead of #!/bin/bash. So when you issue a command from a shellscript, that command must be free from quotes except in places where the quoted material is intentionally one string. 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
