diff options
| -rw-r--r-- | README.md | 27 |
1 files changed, 18 insertions, 9 deletions
@@ -211,12 +211,12 @@ John Black is my name. ```shell case $var in - *sub_string*) + *sub_string1*) # Do stuff ;; *sub_string2*) - # Do more stuff + # Do other stuff ;; *) @@ -231,12 +231,12 @@ esac ```shell case $var in - sub_string*) + sub_string1*) # Do stuff ;; sub_string2*) - # Do more stuff + # Do other stuff ;; *) @@ -251,12 +251,12 @@ esac ```shell case $var in - *sub_string) + *sub_string1) # Do stuff ;; *sub_string2) - # Do more stuff + # Do other stuff ;; *) @@ -411,10 +411,12 @@ Alternative to the `head` command. head() { # Usage: head "n" "file" while read -r line; do - [ "$i" = "$1" ] && break printf '%s\n' "$line" i=$((i+1)) + [ "$i" = "$1" ] && return done < "$2" + + [ -n "$line" ] && printf %s "$line" } ``` @@ -438,7 +440,7 @@ Alternative to `wc -l`. ```sh lines() { # Usage: lines "file" - while read -r _; do + while read -r line || [ -n "$line" ]; do lines=$((lines+1)) done < "$1" @@ -457,6 +459,8 @@ $ lines ~/.bashrc This works by passing the output of the glob to the function and then counting the number of arguments. +**CAVEAT:** When the glob does not match anything (empty directory or no matching files) it is not expanded and the function returns `1`. + **Example Function:** ```sh @@ -584,7 +588,7 @@ done ## Loop over the contents of a file ```shell -while read -r line; do +while read -r line || [ -n "$line" ]; do printf '%s\n' "$line" done < "file" ``` @@ -593,19 +597,24 @@ done < "file" Don’t use `ls`. +**CAVEAT:** When the glob does not match anything (empty directory or no matching files) the variable will contain the unexpanded glob. To avoid working on unexpanded globs check the existence of the file contained in the variable using the appropriate [file conditional](#file-conditionals). Be aware that symbolic links are resolved. + ```shell # Greedy example. for file in *; do + [ -e "$file" ] || [ -L "$file" ] || continue printf '%s\n' "$file" done # PNG files in dir. for file in ~/Pictures/*.png; do + [ -f "$file" ] || continue printf '%s\n' "$file" done # Iterate over directories. for dir in ~/Downloads/*/; do + [ -d "$dir" ] || continue printf '%s\n' "$dir" done ``` |