Differences between revisions 12 and 13
Revision 12 as of 2009-12-24 03:01:24
Size: 2250
Editor: GreyCat
Comment: fix links; remove some already-well-answered questions
Revision 13 as of 2023-06-23 18:14:11
Size: 2399
Editor: 205
Comment:
Deletions are marked like this. Additions are marked like this.
Line 19: Line 19:
   * Commands in a process substitution ( >(cmd) or <(cmd) ) are definitely run in a subshell (or rather a full-blown background process). I'm not sure I understand what this question is really asking. Maybe it's related to [[BashFAQ/084|FAQ 84]].    * Commands in a process substitution ( >(cmd) or <(cmd) ) are definitely run in a subshell (or rather a full-blown background process). I'm not sure I understand what this question is really asking. Maybe it's related to
 * Which shebang should be used or in which circumstance is one preferred over the other?
  * {{{#!/bin/bash}}}
  * {{{#!/usr/bin/env bash}}}

[[BashFAQ/084|FAQ 84]].

Bash Open Questions

If you want to help with the BashFAQ, you could try to answer one of the following questions. Just answer it, copy it to a new subpage of the BashFAQ page (e.g. BashFAQ/101), and remove the question here.

  • How can I redirect the output of the script to both standard output and a log file?
    • Duplicating fds is not sufficient, because it duplicates the file descriptor number, not the data.
    • But you can still use tee: exec > >(tee log)

  • Somewhere the content of variables in my script lose whitespace.
  • How can I make bash set the xterm title to the command it is currently executing?
    • This can't be done in any straightforward manner because there's no hook in Bash to execute arbitrary code after a user presses Enter but before a command is executed. The DEBUG trap is triggered after each command, and the PS1 variable is triggered when a prompt is displayed, which is also after the command, rather than before.
    • In bash 4, the DEBUG trap is triggered before every command, according to help trap. This is a change from bash 3. So this should be possible in bash 4. Someone just needs to write it up....

  • How to determine Yesterday's date?
    • date -d'yesterday' # GNU date (sufficiently new versions)
    • date -d '1 day ago' # GNU date (all versions I have available to test)
    • date -r $(( $(date +%s) - 86400 )) # OpenBSD date
  • How can I redirect file names using sequential numbers to avoid overwriting existing ones?
    • mv --backup=numbered # requires GNU mv
  • How can I set the output of a command to a variable without executing a subshell (i.e. $() ) or writing to a file and reading it back?
    • I think this does the job, have not had time to test: http://tldp.org/LDP/abs/html/process-sub.html (see also ProcessSubstitution on this site)

      • Commands in a process substitution ( >(cmd) or <(cmd) ) are definitely run in a subshell (or rather a full-blown background process). I'm not sure I understand what this question is really asking. Maybe it's related to

  • Which shebang should be used or in which circumstance is one preferred over the other?
    • #!/bin/bash

    • #!/usr/bin/env bash

FAQ 84.

  • Creating temporary files securely and portably (BashFAQ/062 has a partial answer)

BashOpenQuestions (last edited 2023-06-23 18:42:54 by larryv)