Differences

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--- bash:files:read_a_file [2021/01/26 14:14] – [My text files are broken! They lack their final newlines!] peter
+++ bash:files:read_a_file [2021/01/26 14:19] (current) – [How to keep other commands from "eating" the input] peter
@@ Line 25: / Line 25: @@
-===== How to keep other commands from "eating" the input =====
-Some commands greedily eat up all available data on standard input.  The examples above do not take precautions against such programs.  For example,
-<code bash>
-while read -r line; do
-  cat > ignoredfile
-  printf '%s\n' "$line"
-done < "$file"
-</code>
-will only print the contents of the first line, with the remaining contents going to "ignoredfile", as cat slurps up all available input.
-----
-One workaround is to use a numeric FileDescriptor rather than standard input:
-<code bash>
-# Bash
-while IFS= read -r -u 9 line; do
-  cat > ignoredfile
-  printf '%s\n' "$line"
-done 9< "$file"
-# Note that read -u is not portable to every shell. Use a redirect to ensure it works in any POSIX compliant shell:
-while IFS= read -r line <&9; do
-  cat > ignoredfile
-  printf '%s\n' "$line"
-done 9< "$file"
-</code>
-or:
-<code bash>
-exec 9< "$file"
-while IFS= read -r line <&9; do
-  cat > ignoredfile
-  printf '%s\n' "$line"
-done
-exec 9<&-
-</code>
-This example will wait for the user to type something into the file ignoredfile at each iteration instead of eating up the loop input.
-You might need this, for example, with mencoder which will accept user input if there is any, but will continue silently if there isn't.  Other commands that act this way include ssh and ffmpeg.  Additional workarounds for this are discussed in FAQ #89.