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Diffstat (limited to 'ult/handout.rst')
| -rw-r--r-- | ult/handout.rst | 30 |
1 files changed, 15 insertions, 15 deletions
diff --git a/ult/handout.rst b/ult/handout.rst index 38fd62b..0fdcedb 100644 --- a/ult/handout.rst +++ b/ult/handout.rst @@ -980,7 +980,7 @@ The Command Shell Redirection and Piping ---------------------- -Let's say the contents of ``marks.txt`` are as follows, +Let's say the contents of ``marks1.txt`` are as follows, :: @@ -994,13 +994,13 @@ The solution would be as below :: - $ cut -d " " -f 2- marks.txt | paste -d " " students.txt - + $ cut -d " " -f 2- marks1.txt | paste -d " " students.txt - or :: - $ cut -d " " -f 2- marks.txt > /tmp/m_tmp.txt + $ cut -d " " -f 2- marks1.txt > /tmp/m_tmp.txt $ paste -d " " students.txt m_tmp.txt @@ -1051,7 +1051,7 @@ before. We change the ``-f`` option to ``-c`` :: - $ cut -d " " -c 2- marks.txt > /tmp/m_tmp.txt + $ cut -d " " -c 2- marks1.txt > /tmp/m_tmp.txt This prints an error that says the delimiter option should be used with the fields option only, and you can verify that the ``m_tmp.txt`` file is @@ -1060,7 +1060,7 @@ showing it on the display. :: - $ cut -d " " -f 2- marks.txt 1> /tmp/m_tmp.txt 2> /tmp/m_err.txt + $ cut -d " " -f 2- marks1.txt 1> /tmp/m_tmp.txt 2> /tmp/m_err.txt The above command redirects all the errors to the ``m_err.txt`` file and the output to the ``m_tmp.txt`` file. When redirecting, 1 stands @@ -1084,7 +1084,7 @@ Let us now look at the first solution. :: - $ cut -d " " -f 2- marks.txt | paste -d " " students.txt - + $ cut -d " " -f 2- marks1.txt | paste -d " " students.txt - First of all, the hyphen at the end is to ask the paste command to read the standard input, instead of looking for a FILE. The ``man`` page of ``paste`` @@ -1244,7 +1244,7 @@ We just pipe the previous output to the ``sort`` command. :: - $ cut -d " " -f 2- marks.txt | paste -d " " students.txt -| sort + $ cut -d " " -f 2- marks1.txt | paste -d " " students.txt -| sort Let's say we wished to sort the names, based on the marks in the first subject (first column after the name). ``sort`` command also allows us to @@ -1254,7 +1254,7 @@ is used to specify the field. :: - $ cut -d " " -f 2- marks.txt | paste -d " " students.txt -| sort -t " " -k 2 + $ cut -d " " -f 2- marks1.txt | paste -d " " students.txt -| sort -t " " -k 2 The above command give us a sorted output as required. But, it would be nicer to have the output sorted in the reverse order. ``-r`` option allows @@ -1263,7 +1263,7 @@ to choose a numerical sorting. :: - $ cut -d " " -f 2- marks.txt | paste -d " " students.txt -| sort -t " " -k 2 -rn + $ cut -d " " -f 2- marks1.txt | paste -d " " students.txt -| sort -t " " -k 2 -rn ``grep`` -------- @@ -1282,7 +1282,7 @@ names and search for Anne in that. :: - $ cut -d " " -f 2- marks.txt | paste -d " " students.txt - | grep Anne + $ cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | grep Anne This will give you only the line containing the word Anne as the output. The grep command is by default case-sensitive. So, you wouldn't have got @@ -1292,14 +1292,14 @@ to do case-insensitive searches by using the ``-i`` option. :: - $ cut -d " " -f 2- marks.txt | paste -d " " students.txt - | grep -i Anne + $ cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | grep -i Anne Now, in another scenario, if you wished to print all the lines, which do not contain the word Anne, you could use the ``-v`` option. :: - $ cut -d " " -f 2- marks.txt | paste -d " " students.txt - | grep -iv Anne + $ cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | grep -iv Anne Grep allows you to do more complex searches, for instance searching for sentences starting or ending with a particular pattern and regular @@ -1712,7 +1712,7 @@ We open our editor and save the following text to ``results.sh`` #!/bin/bash mkdir ~/marks - cut -d " " -f 2- marks.txt | paste -d " " students.txt - | sort > ~/marks/results.txt + cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | sort > ~/marks/results.txt We can now run the script, @@ -1746,7 +1746,7 @@ the ``echo`` command. We can edit our ``results.sh`` script, as follows. #!/bin/bash mkdir ~/marks - cut -d " " -f 2- marks.txt | paste -d " " students.txt - | sort > ~/marks/results.txt + cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | sort > ~/marks/results.txt echo "Results generated." Now, on running the script, we get a message on the screen informing us, @@ -1760,7 +1760,7 @@ argument in the command line. We can do so, by editing the file, as below. #!/bin/bash mkdir ~/marks - cut -d " " -f 2- marks.txt | paste -d " " students.txt - | sort > ~/marks/$1 + cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | sort > ~/marks/$1 echo "Results generated." |