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--- bash:files:parse_a_line_from_a_file [2021/01/26 16:35] – created peter
+++ bash:files:parse_a_line_from_a_file [2021/01/26 16:53] (current) – [Method 1] peter
@@ Line 3: / Line 3: @@
 There are many ways of doing this, depending on your needs.
-  * Simply print all lines containing the keyword test:
+----
-    <code bash>grep test file.txt</code>
-  * The same but for many keywords.  Create a file that has all the keywords, one per line and run:
+===== Method 1 =====
-    <code bash>grep -f keywords.txt file.txt</code>
-  * Process a file line by line, exit if the line is found:
+Example file:
-    <code bash>while read line; do echo $line | grep test && break; done < file.txt</code>
-  * Exit with status 1 if the line matches.  Unfortunately, if I remember correctly (not 100% sure), bash only allows you to set return values in functions.  So, to get an exit status you need to use something else.  Perl for example:
-    <code perl>perl -ne '/test/ && exit(1)' file.txt</code>
-  * Though you can't set an exit value, you can still do something similar with bash.  The exit value of the last command run is always saved as $? in bash, that means you can test the value of $? and act accordingly:
-<code bash>
-while read line; do let c++; echo $line | grep test >/dev/null;
-  if [[ $? == 0 ]] ; then echo Match for line $c : $line;
-  else echo No match for line $c; fi
-done < file.txt
-</code>
-===== Another approach to process a file line by line: =====
-<code bash>
-#!/bin/bash
-while IFS='' read -r line || [[ -n "$line" ]]; do
-    echo "Text read from file: $line"
-done < "$1"
-</code>
-===== Another Method =====
-Example file.
 <file>
@@ Line 87: / Line 53: @@
 </code>
+<WRAP info>
+**NOTE:**  The **-f** tests that the file exists.
+Other options include:
+  * **-b file**:  Checks if file is a block special file; if yes, then the condition becomes true.    [ -b $file ].
+  * **-c file**:  Checks if file is a character special file; if yes, then the condition becomes true.    [ -c $file ].
+  * **-d file**:  Checks if file is a directory; if yes, then the condition becomes true.     [ -d $file ].
+  * **-e file**:  Checks if file exists; is true even if file is a directory but exists.  [ -e $file ].
+  * **-f file**:  Checks if file is an ordinary file as opposed to a directory or special file; if yes, then the condition becomes true.  [ -f $file ].
+  * **-g file**:  Checks if file has its set group ID (SGID) bit set; if yes, then the condition becomes true.    [ -g $file ].
+  * **-k file**:  Checks if file has its sticky bit set; if yes, then the condition becomes true.     [ -k $file ].
+  * **-p file**:  Checks if file is a named pipe; if yes, then the condition becomes true.    [ -p $file ].
+  * **-r file**:  Checks if file is readable; if yes, then the condition becomes true.    [ -r $file ].
+  * **-t file**:  Checks if file descriptor is open and associated with a terminal; if yes, then the condition becomes true.  [ -t $file ].
+  * **-s file**:  Checks if file has size greater than 0; if yes, then condition becomes true.    [ -s $file ].
+  * **-u file**:  Checks if file has its Set User ID (SUID) bit set; if yes, then the condition becomes true.     [ -u $file ].
+  * **-w file**:  Checks if file is writable; if yes, then the condition becomes true.    [ -w $file ].
+  * **-x file**:  Checks if file is executable; if yes, then the condition becomes true.  [ -x $file ].
-===== Only get last temperature record =====
+</WRAP>
+----
+===== Only get last temperature record =====
 <code>
 #!/bin/bash
-fil=/home/heyu.log.ttyS0
+fil=/home/temp.log.ttyS0
 if [ -f $fil ]