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--- bash_notes [2022/04/06 22:36] – [list file names within a specific range] raju
+++ bash_notes [2023/12/28 08:49] (current) – [other pages in this wiki] raju
@@ Line 1: / Line 1: @@
 ===== tasks =====
-==== list file names within a specific range ====
+==== dummy ====
-In bash, we can use a "sequence expression" to list files within a specific range. For example
+  * [[list files within a specific range]]
-<code>
+===== dummy =====
-$ echo file{18..21}.txt
+==== other pages in this wiki ====
-file18.txt file19.txt file20.txt file21.txt
+  * [[bash scripting]]
-</code>
+  * [[shell scripting notes]]
-The "sequence expression" takes the form ''{x..y[..incr]}'', where x and y are either integers or single characters, and incr, an optional increment, is an integer. It is part of Bash's brace expansion feature.
+==== useful links ====
+  * https://explainshell.com/ - useful for understanding complex shell commands
+  * https://mywiki.wooledge.org/ArithmeticExpression - Arithmetic Expansion
+  * https://misc.flogisoft.com/bash/tip_colors_and_formatting - escape characters, color prompts, echo colored strings
+  * http://ezprompt.net/ - Easy bash prompt generator
-Ref:
+==== documentation links ====
-  * https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html - documentation on Bash's brace expansion feature.
+  * ignoredups, erasedups - https://www.gnu.org/software/bash/manual/html_node/Bash-Variables.html search for ignoredups .
-  * https://superuser.com/questions/236484/list-files-numbered-in-a-specific-range - where I came across the above snippet. Dennis Williamson's reply is pretty comprehensive; provides alternatives solutions; addresses corner cases; high information density. It is worth reading it end to end.
-Possible usages:
+==== what is the difference between "ls > dirlist 2>&1" and "ls 2>&1 > dirlist"? ====
+The command
-To list files
 <code>
-ls file{18..21}.txt
+ls > dirlist 2>&1
 </code>
+directs both standard output (file descriptor 1) and standard error (file descriptor 2) to the file dirlist, while the command
-Use a for loop to run a command on each of them
 <code>
-for file in file{18..21}.txt
+ls 2>&1 > dirlist
-...
 </code>
+directs only the standard output to file dirlist, because the standard error was made a copy of the standard output before the standard output was redirected to dirlist.
-tags | list file names with a range
+To conclude, the order of redirections is significant.
+Ref:- https://www.gnu.org/software/bash/manual/html_node/Redirections.html -> 5th paragraph.
-===== dummy =====
-==== useful links ====
-  * https://mywiki.wooledge.org/ArithmeticExpression - Arithmetic Expansion
 ===== getopts =====
 ==== useful articles ====