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The example I don’t quite understand is:
cut -d : -f /etc/passwd | tr : \\t
What do the two dots mean : and the two bars \\?
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As well as several programming languages, when writing a String, and there are strings that return a value like:
"\a" --> Sinal sonoro
"\n" --> Quebra de linha
"\t" --> Tabulação horizontal
And in Shellscript the backslash or Arrab works the same, but in this case, every character that is after the Arrab is passed to String.
sh ~: touch my keys # cria os arquivos my e keys
sh ~: touch my\ keys # cria o arquivo my keys
And when you put them in sequence \\, is written to arrab.
sh ~: echo escreve-ndo \\ arrab
#escrevendo \ arrab
Already the :, has a difference where it is employed in the case of cut -d : is creating a delimiter for the information that will be launched.
echo "Saida: Meu texto!!!!" > saida
cut -d : -f 1 saida
#Saida
That is, it will write the content even before the :.
In tr the : represents a character to be replaced.
echo "dados:lista" | tr : \- # dados-lista
But the : in some cases, it can be used to assign null value to files or to a disk.
echo "dados para o arquivo" > arquivo
:>arquivo
cat arquivo
File content will be empty.
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-d := fields separated by : (-f missing list of components to select)tr : '\t'replaces ":" by tabs.cut -d : -f 1,5 /etc/passwd | tr : '\t' para username e nome
– JJoao